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Maize MON 87411 was developed to confer resistance to corn rootworms ( Diabrotica spp.) by the expression of a modified version of the Bacillus thuringiensis cry3Bb1 gene and a DvSnf7 dsRNA expression cassette, and tolerance to glyphosate-containing herbicides by the expression of a CP4 5-enolpyruvylshikimate-3-phosphate synthase ( cp4 epsps ) gene. The molecular characterisation data and bioinformatics analyses did not identify issues requiring assessment for food and feed safety. No statistically significant differences in the agronomic and phenotypic characteristics tested between maize MON 87411 and its conventional counterpart were identified. The compositional analysis of maize MON 87411 did not identify differences that required further assessment except for palmitic acid levels in grains from not treated maize MON 87411. The GMO Panel did not identify safety concerns regarding the toxicity and allergenicity of the Cry3Bb1 and CP4 EPSPS proteins, as expressed in maize MON 87411 and found no evidence that the genetic modification might significantly change the overall allergenicity of maize MON 87411. The nutritional impact of maize MON 87411-derived food and feed is expected to be the same as those derived from the conventional counterpart and non-GM commercial reference varieties. The GMO Panel concludes that maize MON 87411, as described in this application, is nutritionally equivalent to and as safe as the conventional counterpart and the non-GM maize reference varieties tested, and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable maize MON 87411 grains into the environment, maize MON 87411 would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of maize MON 87411. The GMO Panel concludes that maize MON 87411, as described in this application, is as safe as its conventional counterpart and the tested non-GM maize reference varieties with respect to potential effects on human and animal health and the environment., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Maize 4114 was developed through Agrobacterium tumefaciens -mediated transformation to provide protection against certain lepidopteran and coleopteran pests by expression of the Cry1F, Cry34Ab1 and Cry35Ab1 proteins derived from Bacillus thuringiensis , and tolerance to the herbicidal active ingredient glufosinate-ammonium by expression of the PAT protein derived from Streptomyces viridochromogenes . The molecular characterisation data did not identify issues requiring assessment for food/feed safety. None of the compositional, agronomic and phenotypic differences identified between maize 4114 and the non-genetically modified (GM) comparator(s) required further assessment. There were no concerns regarding the potential toxicity and allergenicity of the newly expressed proteins Cry1F, Cry34Ab1, Cry35Ab1 and PAT, and no evidence that the genetic modification might significantly change the overall allergenicity of maize 4114. The nutritional value of food/feed derived from maize 4114 is not expected to differ from that derived from non-GM maize varieties and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable maize 4114 grains into the environment, maize 4114 would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of maize 4114. The genetically modified organism (GMO) Panel concludes that maize 4114 is as safe as the non-GM comparator(s) and non-GM reference varieties with respect to potential effects on human and animal health and the environment in the context of the scope of this application., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The three-event stack cotton GHB614 × LLCotton25 × MON 15985 was produced by conventional crossing to combine three single cotton events, GHB614, LLCotton25 and MON 15985. The EFSA GMO Panel previously assessed the three single events and did not identify safety concerns. No new data on the single events that could lead to modification of the original conclusions on their safety were identified. Based on the molecular, agronomic, phenotypic and compositional characteristics, the combination of the single events and of the newly expressed proteins in the three-event stack cotton did not give rise to food and feed safety or nutritional issues. Food and feed derived from cotton GHB614 × LLCotton25 × MON 15985 are expected to have the same nutritional impact as those derived from the non-GM comparator. In the case of accidental release of viable GHB614 × LLCotton25 × MON 15985 cottonseeds into the environment, this three-event stack cotton would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of cotton GHB614 × LLCotton25 × MON 15985. In conclusion, the GMO Panel considers that cotton GHB614 × LLCotton25 × MON 15985, as described in this application, is as safe as the non-GM comparator with respect to potential effects on human and animal health and the environment., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The GMO Panel was previously not in the position to complete the food/feed safety assessment of maize 5307 due to an inadequate 28-day toxicity study necessary for an appropriate assessment of eCry3.1Ab protein. Following a mandate from the European Commission, the GMO Panel assessed a supplementary 28-day toxicity study in mice on the eCry3.1Ab protein (1,000 mg/kg body weight (bw) per day) to complement its scientific opinion on application EFSA-GMO-DE-2011-95 for the placing on the market of the maize 5307 for food and feed uses, import and processing. The supplementary 28-day toxicity study did not show adverse effects. Taking into account the previous assessment and the new information, the GMO Panel concludes that maize 5307, as assessed in the scientific opinion on application EFSA-GMO-DE-2011-95 (EFSA GMO Panel, 2015) and in the supplementary toxicity study, is as safe and nutritious as its conventional counterpart in the scope of this application., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Maize MON 87403 was developed to increase ear biomass at early reproductive phase through the expression of a modified AtHB17 gene from Arabidopsis thaliana , encoding a plant transcription factor of the HD-Zip II family. The molecular characterisation data and bioinformatic analyses did not identify issues requiring assessment for food and feed safety. No statistically significant differences in the agronomic and phenotypic characteristics tested between maize MON 87403 and its conventional counterpart were identified. The compositional analysis of maize MON 87403 did not identify differences that require further assessment. The GMO Panel did not identify safety concerns regarding the toxicity and allergenicity of the AtHB17∆113 protein, as expressed in maize MON 87403. The nutritional value of food and feed derived from maize MON 87403 is not expected to differ from that of food and feed derived from non-genetically modified (GM) maize varieties. Based on the outcome of the studies considered in the comparative analysis and molecular characterisation, the GMO Panel concludes that maize MON 87403 is as safe and nutritious as the conventional counterpart and the non-GM maize reference varieties tested. In the case of accidental release of viable maize MON 87403 grains into the environment, maize MON 87403 would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of maize MON 87403. In conclusion, the GMO Panel considers that maize MON 87403, as described in this application, is as safe as its conventional counterpart and the tested non-GM maize reference varieties with respect to potential effects on human and animal health and the environment., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

RecQ DNA helicases are genome surveillance proteins found in all kingdoms of life. They are characterized best in humans, as mutations in RecQ genes lead to developmental abnormalities and diseases. To better understand RecQ functions in plants we concentrated on Arabidopsis thaliana and Physcomitrella patens , the model species predominantly used for studies on DNA repair and gene targeting. Phylogenetic analysis of the six P. patens RecQ genes revealed their orthologs in humans and plants. Because Arabidopsis and P. patens differ in their RecQ4 and RecQ6 genes, reporter and deletion moss mutants were generated and gene functions studied in reciprocal cross-species and cross-kingdom approaches. Both proteins can be found in meristematic moss tissues, although at low levels and with distinct expression patterns. Pp RecQ4 is involved in embryogenesis and in subsequent development as demonstrated by sterility of Δ PpRecQ4 mutants and by morphological aberrations. Additionally, Δ PpRecQ4 displays an increased sensitivity to DNA damages and an increased rate of gene targeting. Therefore, we conclude that Pp RecQ4 acts as a repressor of recombination. In contrast, Pp RecQ6 is not obviously important for moss development or DNA repair but does function as a potent enhancer of gene targeting., (© 2018 American Society of Plant Biologists. All rights reserved.)

Following the submission of application EFSA-GMO-RX-007 under Regulation (EC) No 1829/2003 from Monsanto, the Panel on Genetically Modified Organisms of the European Food Safety Authority (GMO Panel) was asked to deliver a scientific risk assessment on the data submitted in the context of the renewal of authorisation application of the herbicide-tolerant and insect-resistant genetically modified maize NK603 x MON810. The data received in the context of this renewal application contained post-market environmental monitoring reports, a systematic search and evaluation of literature, updated bioinformatic analyses, and additional documents or studies performed by or on behalf of the applicant. The GMO Panel assessed these data for possible new hazards, modified exposure or new scientific uncertainties identified during the authorisation period and not previously assessed in the context of the original application. Under the assumption that the DNA sequence of the events in maize NK603 x MON810 considered for renewal is identical to the sequence of the originally assessed events, the GMO Panel concludes that there is no evidence in the renewal application EFSA-GMO-RX-007 for new hazards, modified exposure or scientific uncertainties that would change the conclusions of the original risk assessment on maize NK603 x MON810., (© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The GMO Panel has previously assessed the single events Bt11, 59122, MIR604, 1507 and GA21 as well as different stacked events corresponding to combinations of these events and no safety concerns were identified. In its assessment of the five-event maize stack Bt11 × 59122 × MIR604 × 1507 × GA21 (application EFSA-GMO-DE-2011-99), the GMO Panel also assessed all the subcombinations of these events not previously assessed, including some for which little or no experimental data were provided, including the three-event stack Bt11 × 1507 × GA21. In line with Article 5 of the decision for authorisation of application EFSA-GMO-DE-2011-99, the European Commission received from Syngenta information on the levels of the newly expressed proteins in subcombination Bt11 × 1507 × GA21 and tasked EFSA to analyse these data and to indicate whether they have an impact on the previously issued opinion on the five-event stack Bt11 × 59122 × MIR604 × 1507 × GA21 and its subcombinations. Analyses of the levels of the newly expressed proteins Cry1Ab, PAT, Cry1F and mEPSPS showed that there is no indication of an interaction between the events combined in maize Bt11 × 1507 × GA21 that would affect the levels of the newly expressed proteins. Thus, the GMO Panel is of the opinion that the new information for maize Bt11 × 1507 × GA21 does not alter the conclusions of the scientific opinion on application EFSA-GMO-DE-2011-99., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Following the submission of application EFSA-GMO-RX-004 under Regulation (EC) No 1829/2003 from Bayer CropScience, the Panel on Genetically Modified Organisms of the European Food Safety Authority (GMO Panel) was asked to deliver a scientific risk assessment on the data submitted in the context of the renewal of authorisation application of the genetically modified (GM) herbicide-tolerant oilseed rape MS8, RF3 and MS8×RF3. The data received in the context of this renewal application contain post-market environmental monitoring reports, systematic searches and evaluation of literature, updated bioinformatics analyses, and additional documents or studies performed by or on behalf of the applicant. The GMO Panel assessed these data for possible new hazards, modified exposure or new scientific uncertainties identified during the authorisation period and not previously assessed in the context of the original application. Under the assumption that the DNA sequence of the event in oilseed rape MS8, RF3 and MS8×RF3 considered for renewed authorisation is identical to the sequence of the originally assessed event, the GMO Panel concludes that there is no evidence in the context of this renewal application for new hazards, modified exposure or scientific uncertainties that would change the conclusions of the original risk assessment on oilseed rape MS8, RF3 and MS8×RF3., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

In this opinion, the GMO Panel assessed the four-event stack maize 1507 × 59122 ×  MON810 ×  NK603 and its ten subcombinations, independently of their origin. The GMO Panel previously assessed the four single events combined in this four-event stack maize and five of their combinations and did not identify safety concerns. No new data on the single events or their previously assessed combinations leading to modification of the original conclusions were identified. Based on the molecular, agronomic, phenotypic and compositional characteristics, the combination of the single maize events and of the newly expressed proteins in the four-event stack maize did not give rise to food and feed safety or nutritional issues. The GMO Panel concludes that the four-event stack maize is as safe and as nutritious as its non-GM comparator. In the case of accidental release of viable grains of maize 1507 × 59122 × MON810 × NK603 into the environment, this would not raise environmental safety concerns. For four of the subcombinations not previously assessed, protein expression data were provided and did not indicate an interaction affecting the levels of the newly expressed proteins in these subcombinations. The five subcombinations not previously assessed are expected to be as safe as the single maize events, the previously assessed subcombinations and the four-event stack maize. The GMO Panel considers that post-market monitoring of maize 1507 × 59122 ×MON810 × NK603 and its subcombinations is not necessary. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of maize 1507 × 59122 × MON810 ×NK603 and its subcombinations., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

This document provides guidance for the risk assessment under Regulation (EC) No 1829/2003 of the unintended, adventitious or technically unavoidable presence in food and feed of low level of genetically modified plant material intended for markets other than in the European Union. In this context, the presence at low level is defined to be maximum 0.9% of genetically modified plant material per ingredient. This guidance is intended to assist applicants by indicating which scientific requirements of Annex II of Regulation (EU) No 503/2013 are considered necessary for the risk assessment of the presence at low levels of genetically modified plant material in food and feed., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Following the submission of application EFSA-GMO-RX-006 under Regulation (EC) No 1829/2003 from KWS SAAT SE and Monsanto Company, the Panel on Genetically Modified Organisms of the European Food Safety Authority (GMO Panel) was asked to deliver a scientific risk assessment on the data submitted in the context of the renewal of authorisation application for the herbicide-tolerant genetically modified sugar beet H7-1. The data received in the context of this renewal application contained a systematic search and evaluation of literature, updated bioinformatics analyses and additional documents or studies performed by or on behalf of the applicant. The GMO Panel assessed these data for possible new hazards, modified exposure or new scientific uncertainties identified during the authorisation period and not previously assessed in the context of the original application. Under the assumption that the DNA sequence of the event in sugar beet H7-1 considered for renewal is identical to the originally assessed event, the GMO Panel concludes that there is no evidence in the context of this renewal application for new hazards, modified exposure or scientific uncertainties that would change the conclusions of the original risk assessment on sugar beet H7-1., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Following the submission of application EFSA-GMO-RX-005 under Regulation (EC) No 1829/2003 from Syngenta Crop Protection NV/SA, the Panel on Genetically Modified Organisms of the European Food Safety Authority (GMO Panel) was asked to deliver a scientific risk assessment on the data submitted in the context of the renewal of authorisation application of the herbicide-tolerant genetically modified maize GA21. The data received in the context of this renewal application contained post-market environmental monitoring reports, a systematic search and evaluation of literature, updated bioinformatics analyses, and additional documents or studies performed by or on behalf of the applicant. The GMO Panel assessed these data for possible new hazards, modified exposure or new scientific uncertainties identified during the authorisation period and not previously assessed in the context of the original application. Under the assumption that the DNA sequence of the event in maize GA21 considered for renewal is identical to the corrected sequence of the originally assessed event, the GMO Panel concludes that there is no evidence in the renewal application EFSA-GMO-RX-005 for new hazards, modified exposure or scientific uncertainties that would change the conclusions of the original risk assessment on maize GA21., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The GMO Panel has previously assessed genetically modified (GM) soybean 305423 as a single event and as part of a two-event stack, 305423 × 40-3-2. These soybean events were found to be as safe as their conventional counterparts and other appropriate comparators with respect to potential effects on human and animal health and the environment. On 23 February 2017, European Commission requested EFSA to analyse new nucleic acid sequencing data and updated bioinformatics data for soybean event 305423 and to indicate whether the previous conclusions of the GMO Panel on the previously assessed GM soybeans remain valid. The new sequencing data indicated a four base pair (bp) difference compared to the sequencing data originally provided: one bp located in the genomic 3' flanking region, two bp located in a gene silencing cassette and one bp in a partial promoter. These bp reported as differences in the new nucleic acid sequencing data on soybean event 305423 were already present in the original plant material used for the risk assessment. Thus, with the exception of bioinformatics analyses, including an off-target search with the dsRNA expression cassette, the studies performed for the risk assessment of the single event soybean 305423 and the two-event stack soybean 305423 × 40-3-2 remain valid. The new sequencing data and the bioinformatic analyses performed on the new sequence including the RNAi off-target search, did not give rise to safety issues. Therefore, EFSA concludes that the original risk assessment of the single soybean event 305423 and the two-event stack soybean 305423 × 40-3-2 remains valid., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

In this opinion, the GMO Panel assessed the five-event stack maize MON 87427 × MON 89034 ×1507 × MON 88017 × 59122 and its 25 subcombinations, independently of their origin. The GMO Panel has previously assessed the five single events combined to produce this five-event stack maize and 11 subcombinations of these events and did not identify safety concerns. No new data on the single events or their previously assessed subcombinations, leading to modification of the original conclusions were identified. The combination of the single events and of the newly expressed proteins in the five-event stack maize did not give rise to issues - based on the molecular, agronomic/phenotypic or compositional characteristics - regarding food and feed safety and nutrition. Considering the scope of this application, the known biological function of the newly expressed proteins and the data available for the five-event stack maize and its previously assessed maize subcombinations, the GMO Panel considered that different combinations of the single events would not raise environmental concerns. The GMO Panel concludes that the five-event stack maize is as safe and as nutritious as the non-genetically modified (GM) comparator and the tested non-GM reference varieties in the context of its scope. For the 14 maize subcombinations for which no experimental data were provided, the GMO Panel assessed the likelihood of interactions among the single events, and concluded that their combinations would not raise safety concerns. These maize subcombinations are therefore expected to be as safe as the single events, the previously assessed subcombinations and maize MON 87427 ×MON 89034 × 1507 × MON 88017 × 59122. Since the post-market environmental monitoring plan for the five-event stack maize does not include any provisions for the 14 maize subcombinations not previously assessed, the GMO Panel recommended the applicant to revise the plan accordingly., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

In this opinion, the EFSA Panel on Genetically Modified Organisms (GMO Panel) assessed the three-event stack maize MON 87427 × MON 89034 × NK603 and its three subcombinations, independently of their origin. The GMO Panel has previously assessed the three single events combined to produce this three-event stack maize and did not identify safety concerns. No new data on the single events, leading to modification of the original conclusions on their safety, were identified. Based on the molecular, agronomic, phenotypic and compositional characteristics, the combination of the single maize events and of the newly expressed proteins in the three-event stack maize did not give rise to issues regarding food and feed safety or nutrition. In the case of accidental release of viable grains of maize MON 87427 × MON 89034 × NK603 into the environment, the three-event stack maize would not raise environmental safety concerns. The GMO Panel concludes that the three-event stack maize is as safe and as nutritious as the non-GM comparator and the tested non-GM reference varieties in the context of its scope. The GMO Panel considered that its previous conclusions on the two-event stack maize MON 89034 × NK603 remain valid. For the two maize subcombinations for which no experimental data were provided the GMO Panel assessed the likelihood of interactions among the single events, and concluded that their combination would not raise safety concerns. These two subcombinations are therefore expected to be as safe as the single events, the previously assessed maize MON 89034 × NK603 and maize MON 87427 × MON 89034 × NK603. Since the post-market environmental monitoring plan for the three-event stack maize does not include any provisions for the two subcombinations not previously assessed, the GMO Panel recommended the applicant to revise the plan accordingly., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Following the submission of application EFSA-GMO-RX-003 under Regulation (EC) No 1829/2003 from Pioneer Overseas Corporation and Dow AgroSciences LLC, the Panel on Genetically Modified Organisms of the European Food Safety Authority (GMO Panel) was asked to deliver a scientific risk assessment on the data submitted in the context of the renewal of authorisation application of the insect-resistant genetically modified maize 59122. The data received in the context of this renewal application contained post-market environmental monitoring reports, a systematic search and evaluation of literature, updated bioinformatics analyses, and additional documents or studies performed by or on behalf of the applicant. The GMO Panel assessed these data for possible new hazards, modified exposure or new scientific uncertainties identified during the authorisation period and not previously assessed in the context of the original application. Under the assumption that the DNA sequence of the event in maize 59122 considered for renewal is identical to the corrected sequence of the originally assessed event, the GMO Panel concludes that no new hazards or modified exposure and no new scientific uncertainties were identified that would change the conclusions of the original risk assessment on maize 59122., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

This document provides supplementary guidance on specific topics for the allergenicity risk assessment of genetically modified plants. In particular, it supplements general recommendations outlined in previous EFSA GMO Panel guidelines and Implementing Regulation (EU) No 503/2013. The topics addressed are non-IgE-mediated adverse immune reactions to foods, in vitro protein digestibility tests and endogenous allergenicity. New scientific and regulatory developments regarding these three topics are described in this document. Considerations on the practical implementation of those developments in the risk assessment of genetically modified plants are discussed and recommended, where appropriate., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

RNA expression in plant mitochondria implies a large number of post-transcriptional events in which transcript processing and stabilization are essential. In this study, we analyzed the function of the Arabidopsis mitochondrial stability factor 2 gene (MTSF2) and show that the encoded pentatricopeptide repeat protein is essential for the accumulation of stable nad1 mRNA. The production of mature nad1 requires the assembly of three independent RNA precursors via two trans-splicing reactions. Genetic analyses revealed that the lack of nad1 in mtsf2 mutants results from the specific destabilization of the nad1 exons 2-3 precursor transcript. We further demonstrated that MTSF2 binds to its 3΄ extremity with high affinity, suggesting a protective action by blocking exoribonuclease progression. By defining the 3΄ end of nad1 exons 2-3 precursor, MTSF2 concomitantly determines the 3΄ extremity of the first half of the trans-intron found at the end of the transcript. Therefore, binding of the MTSF2 protein to nad1 exons 2-3 precursor evolved both to stabilize the transcript and to define a 3΄ extremity compatible with the trans-splicing reaction needed to reconstitute mature nad1. We thus reveal that the range of transcripts stabilized by association with protective protein on their 3΄ end concerns also mitochondrial precursor transcripts., (© The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.)

In many plant species, gene dosage is an important cause of phenotype variation. Engineering gene dosage, particularly in polyploid genomes, would provide an efficient tool for plant breeding. The hexaploid oilseed crop Camelina sativa, which has three closely related expressed subgenomes, is an ideal species for investigation of the possibility of creating a large collection of combinatorial mutants. Selective, targeted mutagenesis of the three delta-12-desaturase (FAD2) genes was achieved by CRISPR-Cas9 gene editing, leading to reduced levels of polyunsaturated fatty acids and increased accumulation of oleic acid in the oil. Analysis of mutations over four generations demonstrated the presence of a large variety of heritable mutations in the three isologous CsFAD2 genes. The different combinations of single, double and triple mutants in the T3 generation were isolated, and the complete loss-of-function mutants revealed the importance of delta-12-desaturation for Camelina development. Combinatorial association of different alleles for the three FAD2 loci provided a large diversity of Camelina lines with various lipid profiles, ranging from 10% to 62% oleic acid accumulation in the oil. The different allelic combinations allowed an unbiased analysis of gene dosage and function in this hexaploid species, but also provided a unique source of genetic variability for plant breeding., (© 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.)

Beyond its predominant role in human and animal therapy, the CRISPR-Cas9 system has also become an essential tool for plant research and plant breeding. Agronomic applications rely on the mastery of gene inactivation and gene modification. However, if the knock-out of genes by non-homologous end-joining (NHEJ)-mediated repair of the targeted double-strand breaks (DSBs) induced by the CRISPR-Cas9 system is rather well mastered, the knock-in of genes by homology-driven repair or end-joining remains difficult to perform efficiently in higher plants. In this review, we describe the different approaches that can be tested to improve the efficiency of CRISPR-induced gene modification in plants, which include the use of optimal transformation and regeneration protocols, the design of appropriate guide RNAs and donor templates and the choice of nucleases and means of delivery. We also present what can be done to orient DNA repair pathways in the target cells, and we show how the moss Physcomitrella patens can be used as a model plant to better understand what DNA repair mechanisms are involved, and how this knowledge could eventually be used to define more performant strategies of CRISPR-induced gene knock-in., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Following a request from the European Commission, the Panel on Genetically Modified Organisms of the European Food Safety Authority (GMO Panel) assessed the annual post-market environmental monitoring (PMEM) report for the 2015 growing season of the Cry1Ab-expressing maize event MON 810 provided by Monsanto Europe S.A. The GMO Panel concludes that the insect resistance monitoring data submitted to EFSA do not indicate a decrease in susceptibility of field Iberian populations of corn borers to the Cry1Ab protein during the 2015 season. However, since the methodology for insect resistance monitoring remained unchanged compared to previous PMEM reports, the GMO Panel reiterates its previous recommendations on resistance monitoring to provide sufficient detection sensitivity. Although the farmer alert system to report complaints about product performance could complement the information obtained from the laboratory bioassays, the GMO Panel is currently not in a position to appraise its usefulness, and therefore encourages the consent holder to provide more information on this complementary resistance monitoring tool. The data on general surveillance (GS) do not indicate any unanticipated adverse effects on human and animal health or the environment arising from the cultivation of maize MON 810. The GMO Panel reiterates its previous recommendations on the analysis of farmer questionnaires, and advises the consent holder to provide more detailed information on the conducting and reporting of the literature search in future annual PMEM reports. Moreover, the GMO Panel encourages relevant parties to continue developing a methodological framework to use existing networks in the broader context of environmental monitoring. The GMO Panel concludes that the case-specific monitoring (CSM) and GS activities of maize MON 810 as carried out by the consent holder do not provide evidence that would invalidate previous GMO Panel evaluations on the safety of maize MON 810., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

In this opinion, the GMO Panel assessed the three-event stack oilseed rape (OSR) MON 88302 × MS8 × RF3 and its three subcombinations, independently of their origin. The GMO Panel has previously assessed the single events combined to produce this three-event stack OSR and did not identify safety concerns; no new information that would modify the original conclusions was identified. The combination of the single OSR events and of the newly expressed proteins in the three-event stack OSR does not give rise to food and feed safety and nutrition issues - based on the molecular, agronomic/phenotypic and compositional characteristics. In the case of accidental release of viable OSR MON 88302 × MS8 × RF3 seeds into the environment, the three-event stack OSR would not raise environmental safety concerns. The GMO Panel therefore concluded that the three-event stack OSR is as safe and as nutritious as its conventional counterpart and the tested non-GM reference varieties in the context of the scope of this application. Since no new safety concerns were identified for the previously assessed two-event stack OSR MS8 × RF3, the GMO Panel considered that its previous conclusions on this subcombination remain valid. For the two subcombinations MON 88302 × MS8 and MON 88302 × RF3 for which no experimental data were provided, the GMO Panel assessed the likelihood of interactions among the single events, and concluded that their different combinations would not raise safety concerns. These two subcombinations are therefore expected to be as safe as the single events, the previously assessed OSR MS8 × RF3, and OSR MON 88302 × MS8 × RF3. Since the post-market environmental monitoring plan for the three-event stack OSR does not include any provisions for two subcombinations not previously assessed, the GMO Panel recommended the applicant to revise the plan accordingly., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

In this opinion, the EFSA Panel on Genetically Modified Organisms (GMO) assesses the two-event stack soybean FG72 × A5547-127 for food and feed uses, import and processing. The EFSA GMO Panel previously assessed the two single events combined to produce the two-event stack soybean FG72 × A5547-127 and did not identify safety concerns. No new data on the single events, leading to modification of the original conclusions on their safety, were identified. The molecular, agronomic, phenotypic and compositional data on soybean FG72 × A5547-127 did not give rise to safety concerns and no reason to expect interactions between the single events impacting on the food and feed safety of the two-event stack soybean was identified. Although the EFSA GMO Panel cannot conclude on forage composition, soybean forage is not expected to be imported in a significant amount for use as feed. Considering the routes of exposure and limited exposure levels, the EFSA GMO Panel concludes that soybean FG72 × A5547-127 would not give rise to safety concerns in the event of accidental release of viable seeds into the environment. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of soybean FG72 × A5547-127. The EFSA GMO Panel concludes that soybean FG72 × A5547-127 is as safe as the non-genetically modified (GM) comparator and non-GM soybean reference varieties with respect to potential effects on human and animal health and the environment., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Cotton MON 88701 was developed through Agrobacterium tumefaciens -mediated transformation to express the dicamba mono-oxygenase (DMO) protein, conferring tolerance to dicamba, and the phosphinothricin N -acetyltransferase PAT protein, conferring tolerance to glufosinate ammonium-based herbicides. The molecular characterisation data and bioinformatics analyses did not identify issues requiring further assessment for food/feed safety. The agronomic and phenotypic characteristics tested revealed no relevant differences between cotton MON 88701 and its conventional counterpart. Since complete compositional results were reported for only three sites, the EFSA Panel on Genetically Modified Organisms (GMO Panel) is not in the position to complete the assessment of the compositional analysis. Moreover, as no 28-day toxicity study in rodents on the MON 88701 DMO protein was provided, the GMO Panel is not in the position to complete the safety assessment of this protein in cotton MON 88701. Consequently, the GMO Panel cannot complete the toxicological, allergenicity and nutritional assessment of food/feed derived from cotton MON 88701. The safety assessment identified no concerns regarding the potential toxicity and allergenicity of the PAT protein newly expressed in cotton MON 88701. Considering the routes of exposure and limited exposure levels, the GMO Panel concludes that cotton MON 88701 would not give rise to safety concerns in the event of accidental release of viable seeds into the environment. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of cotton MON 88701. In conclusion, in the absence of an appropriate comparative assessment and an appropriate assessment of the MON 88701 DMO protein, the GMO Panel is not in a position to complete its food/feed risk assessment of cotton MON 88701. The GMO Panel concludes that the cotton MON 88701 is unlikely to have any adverse effect on the environment in the context of the scope of the application., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The EFSA Panel on Genetically Modified Organisms (GMO) has previously assessed the single events Bt11, MIR162, MIR604 and GA21 as well as different stacked events corresponding to combinations of these events. These maize events were found to be as safe as their conventional counterparts and other appropriate comparators with respect to potential effects on human and animal health and the environment. In its assessment of the four-event maize stack Bt11 × MIR162 × MIR604 × GA21, the GMO Panel also assessed all the subcombinations of these events not previously assessed, including some for which little or no experimental data were provided, including the two-stack maize event Bt11 × MIR162 (application EFSA-GMO-DE-2009-66). On 8 November 2016, the European Commission received from Syngenta information on the subcombination Bt11 × MIR162. On 14 December 2016, the European Commission tasked EFSA to analyse these data and to indicate whether they have an impact on the previously issued opinion on the four-event stack Bt11 × MIR162 × MIR604 × GA21 and its subcombinations. The GMO Panel used the appropriate principles described in its guidelines for the risk assessment of genetically modified (GM) plants to analyse the provided data. The levels of the newly expressed proteins Cry1Ab, PAT, Vip3Aa20 and PMI are similar between the two-event stack Bt11 × MIR162 and the corresponding single events Bt11 and MIR162. Based on this analysis, there is no indication of an interaction between the events combined in maize Bt11 × MIR162 that would affect the levels of the newly expressed proteins. Thus, the GMO Panel considers that the new information for maize Bt11 × MIR162 does not alter the conclusions of the scientific opinion on application EFSA-GMO-DE-2009-66., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Soybean DAS-44406-6 expresses 5-enolpyruvyl-shikimate-3-phosphate synthase (2mEPSPS), conferring tolerance to glyphosate-based herbicides, aryloxyalkanoate dioxygenase (AAD-12), conferring tolerance to 2,4-dichlorophenoxyacetic acid (2,4-D) and other related phenoxy herbicides, and phosphinothricin acetyl transferase (PAT), conferring tolerance to glufosinate ammonium-based herbicides. The molecular characterisation data and bioinformatics analyses did not identify issues requiring assessment for food/feed safety. The agronomic and phenotypic characteristics revealed no relevant differences between soybean DAS-44406-6 and its conventional counterpart, except for pod count, seed count and yield. The compositional analysis identified no differences requiring further assessment, except for an increase (up to 31%) in lectin activity in soybean DAS-44406-6. Such increase is unlikely to raise additional concerns for food/feed safety and nutrition of soybean DAS-44406-6 as compared to its conventional counterpart and non-GM reference varieties. There were no concerns regarding the potential toxicity and allergenicity of the three newly expressed proteins, and no evidence that the genetic modification might significantly change the overall allergenicity of soybean DAS-44406-6. Soybean DAS-44406-6 is as nutritious as its conventional counterpart and the non-GM soybean reference varieties tested. There are no indications of an increased likelihood of establishment and spread of occasional feral soybean DAS-44406-6 plants, unless exposed to the intended herbicides. The likelihood of environmental effects from the accidental release of viable seeds from soybean DAS-44406-6 into the environment is therefore very low. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of soybean DAS-44406-6. In conclusion, the GMO Panel considers that the information available for soybean DAS-44406-6 addresses the scientific comments raised by Member States and that soybean DAS-44406-6, as described in this application, is as safe as its conventional counterpart and non-GM soybean reference varieties with respect to potential effects on human and animal health and the environment in the context of the scope of this application., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Soybean DAS-68416-4 was developed by Agrobacterium tumefaciens -mediated transformation to express the aryloxyalkanoate dioxygenase-12 (AAD-12) protein, conferring tolerance to 2,4-dichlorophenoxyacetic acid (2,4-D) and other related phenoxy herbicides, and the phosphinothricin acetyltransferase (PAT) protein, conferring tolerance to glufosinate ammonium-based herbicides. The molecular characterisation data and bioinformatics analyses did not identify issues requiring further assessment for food/feed safety. The agronomic and phenotypic characteristics tested revealed no relevant differences between soybean DAS-68416-4 and its conventional counterpart, except for 'days to 50% flowering'. The compositional analysis identified no differences requiring further assessment, except for an increase (up to 36%) in lectin activity in soybean DAS-68416-4. Such increase is unlikely to raise additional concerns for food/feed safety and nutrition for soybean DAS-68416-4 as compared to its conventional counterpart and the non-GM reference varieties. There were no concerns regarding the potential toxicity and allergenicity of the two newly expressed proteins, and no evidence that the genetic modification might significantly change the overall allergenicity of soybean DAS-68416-4. Soybean DAS-68416-4 is as nutritious as its conventional counterpart and the non-GM reference varieties. There are no indications of an increased likelihood of establishment and spread of occasional feral soybean DAS-68416-4 plants, unless these are exposed to the intended herbicides. The likelihood of environmental effects resulting from the accidental release of viable seeds from soybean DAS-68416-4 into the environment is therefore very low. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of soybean DAS-68416-4. The GMO Panel concludes that the information available addresses the scientific comments of the Member States and that soybean DAS-68416-4, as described in this application, is as safe as its conventional counterpart and the tested non-GM reference varieties with respect to potential effects on human and animal health and the environment in the context of the scope of this application., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The European Commission mandated EFSA to review a new data package provided by the company Elanco, for the possible integration/non-integration of the DNA plasmid vaccine CLYNAV into the genome of Atlantic salmon ( Salmo salar ) and to indicate whether EFSA agrees with the conclusions drawn by Elanco. The vaccine is injected into fish to confer protection against pancreas disease caused by the salmonid alphavirus. The majority of the experimental data provided by the company was for muscle tissue close to the injection site and for gonadal tissue. EFSA considers that the long persistence of DNA plasmid in muscle tissue close to the injection site and the potential heritability of an integration event in gonad cells support the focus of the assessment on both these tissues. The experimental data did not provide scientifically robust evidence for a true integration event. The company overall concluded that the likelihood of integration is negligible, based on considerations in the context of the company's environmental risk assessment, but did not provide a quantitative value for the rate of integration linked to the term 'negligible'. It is therefore not possible to evaluate this statement specifically with regard to integration rates. EFSA notes that knowledge about homologous and non-homologous integration predicts that integration could occur with certain frequency. Therefore, EFSA has constructed worst-case scenarios leading to upper estimates for possible integration rates of the DNA plasmid vaccine into the Atlantic salmon genome. EFSA concludes that, based on the worst-case scenarios described here and taking into account additional factors decreasing the likelihood of integration, the actual integration rate is likely to be orders of magnitude lower than the upper estimated integration rate calculated in the context of the worst-case scenarios. With the available evidence, the actual integration rate cannot be estimated with more precision., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Following the submission of application EFSA-GMO-RX-001 under Regulation (EC) No 1829/2003 from Pioneer Overseas Corporation and Dow Agrosciences LLC, the Panel on Genetically Modified Organisms of the European Food Safety Authority (GMO Panel) was asked to deliver a scientific risk assessment on the data submitted in the frame of a renewal of authorisation application of the insect-resistant and herbicide-tolerant genetically modified (GM) maize 1507. The data package received in the frame of this renewal application contained post-market environmental monitoring reports, a systematic search and evaluation of literature, an updated bioinformatics analysis and additional documents or studies performed by or on behalf of the applicant. The GMO Panel assessed this data package for possible new hazards, modified exposure or new scientific uncertainties identified during the authorisation period and not previously assessed in the frame of the original application. Under the assumption that the DNA sequence of the event in maize 1507 considered for renewal is identical to the corrected sequence of the originally assessed event, the GMO Panel concludes that no new hazards or modified exposure and no new scientific uncertainties were identified for the application for renewal that would change the conclusions of the original risk assessment on maize 1507 (EFSA, 2005b, 2009)., (© 2017 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

The ability to address the CRISPR-Cas9 nuclease complex to any target DNA using customizable single-guide RNAs has now permitted genome engineering in many species. Here, we report its first successful use in a nonvascular plant, the moss Physcomitrella patens. Single-guide RNAs (sgRNAs) were designed to target an endogenous reporter gene, PpAPT, whose inactivation confers resistance to 2-fluoroadenine. Transformation of moss protoplasts with these sgRNAs and the Cas9 coding sequence from Streptococcus pyogenes triggered mutagenesis at the PpAPT target in about 2% of the regenerated plants. Mainly, deletions were observed, most of them resulting from alternative end-joining (alt-EJ)-driven repair. We further demonstrate that, in the presence of a donor DNA sharing sequence homology with the PpAPT gene, most transgene integration events occur by homology-driven repair (HDR) at the target locus but also that Cas9-induced double-strand breaks are repaired with almost equal frequencies by mutagenic illegitimate recombination. Finally, we establish that a significant fraction of HDR-mediated gene targeting events (30%) is still possible in the absence of PpRAD51 protein, indicating that CRISPR-induced HDR is only partially mediated by the classical homologous recombination pathway., (© 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.)

Powerful genome editing technologies are needed for efficient gene function analysis. The CRISPR-Cas9 system has been adapted as an efficient gene-knock-out technology in a variety of species. However, in a number of situations, knocking out or modifying a single gene is not sufficient; this is particularly true for genes belonging to a common family, or for genes showing redundant functions. Like many plants, the model organism Physcomitrella patens has experienced multiple events of polyploidization during evolution that has resulted in a number of families of duplicated genes. Here, we report a robust CRISPR-Cas9 system, based on the codelivery of a CAS9 expressing cassette, multiple sgRNA vectors, and a cassette for transient transformation selection, for gene knock-out in multiple gene families. We demonstrate that CRISPR-Cas9-mediated targeting of five different genes allows the selection of a quintuple mutant, and all possible subcombinations of mutants, in one experiment, with no mutations detected in potential off-target sequences. Furthermore, we confirmed the observation that the presence of repeats in the vicinity of the cutting region favors deletion due to the alternative end joining pathway, for which induced frameshift mutations can be potentially predicted. Because the number of multiple gene families in Physcomitrella is substantial, this tool opens new perspectives to study the role of expanded gene families in the colonization of land by plants., (Copyright © 2016 Lopez-Obando et al.)

Because of its highly efficient homologous recombination, the moss Physcomitrella patens is a model organism particularly suited for reverse genetics, but this inherent characteristic limits forward genetic approaches. Here, we show that the tobacco (Nicotiana tabacum) retrotransposon Tnt1 efficiently transposes in P. patens, being the first retrotransposon from a vascular plant reported to transpose in a bryophyte. Tnt1 has a remarkable preference for insertion into genic regions, which makes it particularly suited for gene mutation. In order to stabilize Tnt1 insertions and make it easier to select for insertional mutants, we have developed a two-component system where a mini-Tnt1 with a retrotransposition selectable marker can only transpose when Tnt1 proteins are co-expressed from a separate expression unit. We present a new tool with which to produce insertional mutants in P. patens in a rapid and straightforward manner that complements the existing molecular and genetic toolkit for this model species., (© 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.)

Key Message: New tools for the precise modification of crops genes are now available for the engineering of new ideotypes. A future challenge in this emerging field of genome engineering is to develop efficient methods for allele mining. Genome engineering tools are now available in plants, including major crops, to modify in a predictable manner a given gene. These new techniques have a tremendous potential for a spectacular acceleration of the plant breeding process. Here, we discuss how genetic diversity has always been the raw material for breeders and how they have always taken advantage of the best available science to use, and when possible, increase, this genetic diversity. We will present why the advent of these new techniques gives to the breeders extremely powerful tools for crop breeding, but also why this will require the breeders and researchers to characterize the genes underlying this genetic diversity more precisely. Tackling these challenges should permit the engineering of optimized alleles assortments in an unprecedented and controlled way.

While the molecular basis for cytokinin action is quite well understood in flowering plants, little is known about the cytokinin signal transduction in early diverging land plants. The genome of the bryophyte Physcomitrella patens (Hedw.) B.S. encodes three classical cytokinin receptors, the CHASE domain-containing histidine kinases, CHK1, CHK2, and CHK3. In a complementation assay with protoplasts of receptor-deficient Arabidopsis thaliana as well as in cytokinin binding assays, we found evidence that CHK1 and CHK2 receptors can function in cytokinin perception. Using gene targeting, we generated a collection of CHK knockout mutants comprising single (Δchk1, Δchk2, Δchk3), double (Δchk1,2, Δchk1,3, Δchk2,3), and triple (Δchk1,2,3) mutants. Mutants were characterized for their cytokinin response and differentiation capacities. While the wild type did not grow on high doses of cytokinin (1 µM benzyladenine), the Δchk1,2,3 mutant exhibited normal protonema growth. Bud induction assays showed that all three cytokinin receptors contribute to the triggering of budding, albeit to different extents. Furthermore, while the triple mutant showed no response in this bioassay, the remaining mutants displayed budding responses in a diverse manner to different types and concentrations of cytokinins. Determination of cytokinin levels in mutants showed no drastic changes for any of the cytokinins; thus, in contrast to Arabidopsis, revealing only small impacts of cytokinin signaling on homeostasis. In summary, our study provides a first insight into the molecular action of cytokinin in an early diverging land plant and demonstrates that CHK receptors play an essential role in bud induction and gametophore development., (© The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

RNAi offers opportunities to generate new traits in genetically modified (GM) plants. Instead of expressing novel proteins, RNAi-based GM plants reduce target gene expression. Silencing of off-target genes may trigger unintended effects, and identifying these genes would facilitate risk assessment. However, using bioinformatics alone is not reliable, due to the lack of genomic data and insufficient knowledge of mechanisms governing mRNA-small (s)RNA interactions., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The eukaryotic RecA homologue Rad51 is a key factor in homologous recombination and recombinational repair. Rad51-like proteins have been identified in yeast (Rad55, Rad57 and Dmc1), plants and vertebrates (RAD51B, RAD51C, RAD51D, XRCC2, XRCC3 and DMC1). RAD51 and DMC1 are the strand-exchange proteins forming a nucleofilament for strand invasion, however, the function of the paralogues in the process of homologous recombination is less clear. In yeast the two Rad51 paralogues, Rad55 and Rad57, have been shown to be involved in somatic and meiotic HR and they are essential to the formation of the Rad51/DNA nucleofilament counterbalancing the anti-recombinase activity of the SRS2 helicase. Here, we examined the role of RAD51B in the model bryophyte Physcomitrella patens. Mutant analysis shows that RAD51B is essential for the maintenance of genome integrity, for resistance to DNA damaging agents and for gene targeting. Furthermore, we set up methods to investigate meiosis in Physcomitrella and we demonstrate that the RAD51B protein is essential for meiotic homologous recombination. Finally, we show that all these functions are independent of the SRS2 anti-recombinase protein, which is in striking contrast to what is found in budding yeast where the RAD51 paralogues are fully dependent on the SRS2 anti-recombinase function., (© The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Nucleocytoplasmic large DNA viruses (NCLDVs) are eukaryotic viruses with large genomes (100 kb-2.5 Mb), which include giant Mimivirus, Megavirus and Pandoravirus. NCLDVs are known to infect animals, protists and phytoplankton but were never described as pathogens of land plants. Here, we show that the bryophyte Physcomitrella patens and the lycophyte Selaginella moellendorffii have open reading frames (ORFs) with high phylogenetic affinities to NCLDV homologues. The P. patens genes are clustered in DNA stretches (up to 13 kb) containing up to 16 NCLDV-like ORFs. Molecular evolution analysis suggests that the NCLDV-like regions were acquired by horizontal gene transfer from distinct but closely related viruses that possibly define a new family of NCLDVs. Transcriptomics and DNA methylation data indicate that the NCLDV-like regions are transcriptionally inactive and are highly cytosine methylated through a mechanism not relying on small RNAs. Altogether, our data show that members of NCLDV have infected land plants.

Conventional plant breeding exploits existing genetic variability and introduces new variability by mutagenesis. This has proven highly successful in securing food supplies for an ever-growing human population. The use of genetically modified plants is a complementary approach but all plant breeding techniques have limitations. Here, we discuss how the recent evolution of targeted mutagenesis and DNA insertion techniques based on tailor-made site-directed nucleases (SDNs) provides opportunities to overcome such limitations. Plant breeding companies are exploiting SDNs to develop a new generation of crops with new and improved traits. Nevertheless, some technical limitations as well as significant uncertainties on the regulatory status of SDNs may challenge their use for commercial plant breeding., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

In this chapter, we review the main organogenesis features and associated regulation processes of the moss Physcomitrella patens (P. patens), the model plant for the Bryophytes. We highlight how the study of this descendant of the earliest plant species that colonized earth, brings useful keys to understand the mechanisms that determine and control both vascular and non vascular plants organogenesis. Despite its simple morphogenesis pattern, P. patens still requires the fine tuning of organogenesis regulators, including hormone signalling, common to the whole plant kingdom, and which study is facilitated by a high number of molecular tools, among which the powerful possibility of gene targeting/replacement. The recent discovery of moss cells reprogramming capacity completes the picture of an excellent model for studying plant organogenesis.

The moss Physcomitrella patens is unique among plant models for the high frequency with which targeted transgene insertion occurs via homologous recombination. Transgene integration is believed to utilize existing machinery for the detection and repair of DNA double-strand breaks (DSBs). We undertook targeted knockout of the Physcomitrella genes encoding components of the principal sensor of DNA DSBs, the MRN complex. Loss of function of PpMRE11 or PpRAD50 strongly and specifically inhibited gene targeting, whilst rates of untargeted transgene integration were relatively unaffected. In contrast, disruption of the PpNBS1 gene retained the wild-type capacity to integrate transforming DNA efficiently at homologous loci. Analysis of the kinetics of DNA-DSB repair in wild-type and mutant plants by single-nucleus agarose gel electrophoresis revealed that bleomycin-induced fragmentation of genomic DNA was repaired at approximately equal rates in each genotype, although both the Ppmre11 and Pprad50 mutants exhibited severely restricted growth and development and enhanced sensitivity to UV-B and bleomycin-induced DNA damage, compared with wild-type and Ppnbs1 plants. This implies that while extensive DNA repair can occur in the absence of a functional MRN complex; this is unsupervised in nature and results in the accumulation of deleterious mutations incompatible with normal growth and development.

The shoot represents the basic body plan in land plants. It consists of a repeated structure composed of stems and leaves. Whereas vascular plants generate a shoot in their diploid phase, non-vascular plants such as mosses form a shoot (called the gametophore) in their haploid generation. The evolution of regulatory mechanisms or genetic networks used in the development of these two kinds of shoots is unclear. TERMINAL EAR1-like genes have been involved in diploid shoot development in vascular plants. Here, we show that disruption of PpTEL1 from the moss Physcomitrella patens, causes reduced protonema growth and gametophore initiation, as well as defects in gametophore development. Leafy shoots formed on ΔTEL1 mutants exhibit shorter stems with more leaves per shoot, suggesting an accelerated leaf initiation (shortened plastochron), a phenotype shared with the Poaceae vascular plants TE1 and PLA2/LHD2 mutants. Moreover, the positive correlation between plastochron length and leaf size observed in ΔTEL1 mutants suggests a conserved compensatory mechanism correlating leaf growth and leaf initiation rate that would minimize overall changes in plant biomass. The RNA-binding protein encoded by PpTEL1 contains two N-terminus RNA-recognition motifs, and a third C-terminus non-canonical RRM, specific to TEL proteins. Removal of the PpTEL1 C-terminus (including this third RRM) or only 16-18 amino acids within it seriously impairs PpTEL1 function, suggesting a critical role for this third RRM. These results show a conserved function of the RNA-binding PpTEL1 protein in the regulation of shoot development, from early ancestors to vascular plants, that depends on the third TEL-specific RRM.

Strigolactones are a novel class of plant hormones controlling shoot branching in seed plants. They also signal host root proximity during symbiotic and parasitic interactions. To gain a better understanding of the origin of strigolactone functions, we characterised a moss mutant strongly affected in strigolactone biosynthesis following deletion of the CAROTENOID CLEAVAGE DIOXYGENASE 8 (CCD8) gene. Here, we show that wild-type Physcomitrella patens produces and releases strigolactones into the medium where they control branching of protonemal filaments and colony extension. We further show that Ppccd8 mutant colonies fail to sense the proximity of neighbouring colonies, which in wild-type plants causes the arrest of colony extension. The mutant phenotype is rescued when grown in the proximity of wild-type colonies, by exogenous supply of synthetic strigolactones or by ectopic expression of seed plant CCD8. Thus, our data demonstrate for the first time that Bryophytes (P. patens) produce strigolactones that act as signalling factors controlling developmental and potentially ecophysiological processes. We propose that in P. patens, strigolactones are reminiscent of quorum-sensing molecules used by bacteria to communicate with one another.

Cloning through seeds has potential revolutionary applications in agriculture, because it would allow vigorous hybrids to be propagated indefinitely. However, asexual seed formation or apomixis, avoiding meiosis and fertilization, is not found in the major food crops. To develop de novo synthesis of apomixis, we crossed Arabidopsis MiMe and dyad mutants that produce diploid clonal gametes to a strain whose chromosomes are engineered to be eliminated after fertilization. Up to 34% of the progeny were clones of their parent, demonstrating the conversion of clonal female or male gametes into seeds. We also show that first-generation cloned plants can be cloned again. Clonal reproduction through seeds can therefore be achieved in a sexual plant by manipulating two to four conserved genes.

Meiotic recombination is initiated by the formation of numerous DNA double-strand breaks (DSBs) catalysed by the widely conserved Spo11 protein. In Saccharomyces cerevisiae, Spo11 requires nine other proteins for meiotic DSB formation; however, unlike Spo11, few of these are conserved across kingdoms. In order to investigate this recombination step in higher eukaryotes, we took advantage of a high-throughput meiotic mutant screen carried out in the model plant Arabidopsis thaliana. A collection of 55,000 mutant lines was screened, and spo11-like mutations, characterised by a drastic decrease in chiasma formation at metaphase I associated with an absence of synapsis at prophase, were selected. This screen led to the identification of two populations of mutants classified according to their recombination defects: mutants that repair meiotic DSBs using the sister chromatid such as Atdmc1 or mutants that are unable to make DSBs like Atspo11-1. We found that in Arabidopsis thaliana at least four proteins are necessary for driving meiotic DSB repair via the homologous chromosomes. These include the previously characterised DMC1 and the Hop1-related ASY1 proteins, but also the meiotic specific cyclin SDS as well as the Hop2 Arabidopsis homologue AHP2. Analysing the mutants defective in DSB formation, we identified the previously characterised AtSPO11-1, AtSPO11-2, and AtPRD1 as well as two new genes, AtPRD2 and AtPRD3. Our data thus increase the number of proteins necessary for DSB formation in Arabidopsis thaliana to five. Unlike SPO11 and (to a minor extent) PRD1, these two new proteins are poorly conserved among species, suggesting that the DSB formation mechanism, but not its regulation, is conserved among eukaryotes., Competing Interests: The authors have declared that no competing interests exist.

The moss Physcomitrella patens is a long-standing model for studying plant development, growth and cell differentiation in particular. Interest in this non-vascular plant arose following the discovery that homologous recombination is an efficient process. P. patens is, therefore, a tool of choice not only to study gene function but also for recombinant protein production. This system has many attributes that are advantageous for molecular farming: protein production in cell suspension, the possibility of generating targeted knockout mutants for glycoengineering and quantitative optimization for protein production. In terms of technical advances, P. patens is one of the most up-to-date plant expression systems and is a promising alternative to animal cell factories for the production of therapeutic proteins with either simple or highly complex structures.

The reappearance of HTH alleles in the offspring of homozygous Arabidopsis hth mutants is not consistent with classical Mendelian genetics. It has been suggested that stored RNA may be used to restore genetic information. However, Peng et al. reported that hth mutants tend to display outcrossing and suggested that outcrossing might provide an alternative explanation for the apparent genetic instability. We have confirmed and extended these results, corroborating that the apparent non-Mendelian behavior of hth mutants can be explained by their susceptibility to outcrossing.

Although aquaporins (AQPs) have been shown to increase membrane water permeability in many cell types, the physiological role of this increase was not always obvious. In this report, we provide evidence that in the leafy stage of development (gametophore) of the moss Physcomitrella patens, AQPs help to replenish more rapidly the cell water that is lost by transpiration, at least if some water is in the direct vicinity of the moss plant. Three AQP genes were cloned in P. patens: PIP2;1, PIP2;2, and PIP2;3. The water permeability of the membrane was measured in protoplasts from leaves and protonema. A significant decrease was measured in protoplasts from leaves and protonema of PIP2;1 or PIP2;2 knockouts but not the PIP2;3 knockout. No phenotype was observed when knockout plants were grown in closed petri dishes with ample water supply. Gametophores isolated from the wild type and the pip2;3 mutant were not sensitive to moderate water stress, but pip2;1 or pip2;2 gametophores expressed a water stress phenotype. The knockout mutant leaves were more bent and twisted, apparently suffering from an important loss of cellular water. We propose a model to explain how the AQPs PIP2;1 and PIP2;2 delay leaf dessication in a drying atmosphere. We suggest that in ancestral land plants, some 400 million years ago, APQs were already used to facilitate the absorption of water.

The moss, Physcomitrella patens, is a novel tool in plant functional genomics due to its exceptionally high gene targeting efficiency that is so far unique for plants. To determine if this high gene targeting efficiency is exclusive to P. patens or if it is a common feature to mosses, we estimated gene-targeting efficiency in another moss, Ceratodon purpureus. We transformed both mosses with replacement vectors corresponding to the adenine phosphoribosyl transferase (APT) reporter gene. We achieved a gene targeting efficiency of 20.8% for P. patens and 1.05% for C. purpureus. Our findings support the hypothesis that efficient gene targeting could be a general mechanism of Bryophyte transformation.

MSH2 is a central component of the mismatch repair pathway that targets mismatches arising during DNA replication, homologous recombination (HR) and in response to genotoxic stresses. Here, we describe the function of MSH2 in the moss Physcomitrella patens, as deciphered by the analysis of loss of function mutants. Ppmsh2 mutants display pleiotropic growth and developmental defects, which reflect genomic instability. Based on loss of function of the APT gene, we estimated this mutator phenotype to be at least 130 times higher in the mutants than in wild type. We also found that MSH2 is involved in some but not all the moss responses to genotoxic stresses we tested. Indeed, the Ppmsh2 mutants were more tolerant to cisplatin and show higher sensitivity to UV-B radiations. PpMSH2 gene involvement in HR was studied by assessing gene targeting (GT) efficiency with homologous and homeologous sequences. GT efficiency with homologous sequences was slightly decreased in the Ppmsh2 mutant compared with wild type. Strikingly GT efficiency with homeologous sequences decreased proportionally to sequence divergence in the wild type whereas it remained unaffected in the mutants. Those results demonstrate the role of PpMSH2 in the maintenance of genome integrity and in homologous and homeologous recombination.