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KNOTTED1-like homeobox (KNOX) genes serve important roles in meristem function and many developmental processes in all higher plants. In Arabidopsis, studies of KNOX genes especially among members of class II KNOX genes remain limited and functional data are largely lacking. In the present study, we established a reproducible protocol that is important for genetic studies of KNOX genes using Arabidopsis insertional mutants. This protocol contains a reproducible and serial procedure containing detailed and step-by-step laboratory and field works covering all experiment steps from the screening of homozygous mutant lines to the KNOX expression analysis using qRT-PCR in a single paper. The troubleshooting and challenges that might occur are also presented and discussed. T-DNA insertion mutants for all Arabidopsis KNOX genes (except for knat4) were isolated based on kanamycin screening, phenotype selection, and PCR genotyping. Surprisingly, the insertions resulted in strong repression of the respective KNOX genes. However, no gene suppression was observed for the positively selected knat5 mutant. Moreover, qRT-PCR was effective for transcript analysis among the knox mutant samples. The use of different relative expression quantification produces a similar indication of expression level. Overall, the proposed procedure is highly effective for expression studies of KNOX genes in Arabidopsis mutants and will serve as a fundamental work protocol to open opportunities for genetic studies of genes involving insertional mutants in Arabidopsis. [ABSTRACT FROM AUTHOR]

Summary : Nowadays, little information is available regarding the N‐glycosylation pathway in the green microalga Chlamydomonas reinhardtii. Recent investigation demonstrated that C. reinhardtii synthesizes linear oligomannosides. Maturation of these oligomannosides results in N‐glycans that are partially methylated and carry one or two xylose residues. One xylose residue was demonstrated to be a core β(1,2)‐xylose. Recently, N‐glycoproteomic analysis performed on glycoproteins secreted by C. reinhardtii demonstrated that the xylosyltransferase A (XTA) was responsible for the addition of the core β(1,2)‐xylose. Furthermore, another xylosyltransferase candidate named XTB was suggested to be involved in the xylosylation in C. reinhardtii. In the present study, we focus especially on the characterization of the structures of the xylosylated N‐glycans from C. reinhardtii taking advantage of insertional mutants of XTA and XTB, and of the XTA/XTB double‐mutant. The combination of mass spectrometry approaches allowed us to identify the major N‐glycan structures bearing one or two xylose residues. They confirm that XTA is responsible for the addition of the core β(1,2)‐xylose, whereas XTB is involved in the addition of the xylose residue onto the linear branch of the N‐glycan as well as in the partial addition of the core β(1,2)‐xylose suggesting that this transferase exhibits a low substrate specificity. Analysis of the double‐mutant suggests that an additional xylosyltransferase is involved in the xylosylation process in C. reinhardtii. Additional putative candidates have been identified in the C. reinhardtii genome. Altogether, these results pave the way for a better understanding of the C. reinhardtii N‐glycosylation pathway. Significance Statement: Xylosylation in Chlamydomonas reinhardtii leads to heterogeneous N‐glycan structures. XTA is responsible for the addition of core β(1,2)‐xylose, whereas XTB could be involved in the addition of xylose residue onto the linear branch of the N‐glycan and in complement to XTA, in the partial addition of the core β(1,2)‐xylose, suggesting that this transferase exhibits a low acceptor substrate specificity. Additional XT candidates are involved in the xylosylation process in C. reinhardtii. [ABSTRACT FROM AUTHOR]

Abstract Background The unicellular green alga, Chlamydomonas reinhardtii, is a classic model for studying flagella and biofuel. However, precise gene editing, such as Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated protein (Cas9) system, is not widely used in this organism. Screening of random insertional mutant libraries by polymerase chain reaction provides an alternate strategy to obtain null mutants of individual gene. But building, screening, and maintaining such a library was time-consuming and expensive. Results By selecting a suitable parental strain, keeping individual mutants using the agar plate, and designing an insertion cassette-specific primer for library screening, we successfully generated and maintained ~150,000 insertional mutants of Chlamydomonas, which was used for both reverse and forward genetics analysis. We obtained 26 individual mutants corresponding to 20 genes and identified 967 motility-defect mutants including 10 mutants with defective accumulation of intraflagellar transport complex at the basal body. We also obtained 929 mutants defective in oil droplet assembly after nitrogen deprivation. Furthermore, a new insertion cassette with splicing donor sequences at both ends was also constructed, which increased the efficiency of gene interruption. Conclusion In summary, this library provides a multifunctional platform both for obtaining mutants of interested genes and for screening of mutants with specific phenotype.

Avirulent B. pertussis bacteria containing IS elements in the bvgAS operon were detected during the study of whooping cough patients and bacilli carriers. The present work is devoted to the study of the accumulation dynamics and the mechanisms of generation of persistent forms of the B. pertussis bacteria in lower monkeys as the most adequate model for extrapolation of the experiment results to humans. By means of the real-time PCR method, it was established that the B. pertussis bacteria lived more than three months in the upper respiratory tract after a single intranasal monkey infection; the period was reduced to 14-28 days during repeated infection. An increase in the portion of B. pertussis Bvg mutants in the population to tens of percent from the total number of registered bacteria was registered. The experimental confirmation of the development and accumulation of avirulent B. pertussis Bvg mutants during the development of the infectious process was obtained. Further study of the composition of the B. pertussis persistent bacteria population at different stages of the disease will make it possible to formulate new approaches to the whooping cough diagnostics and prevention and creation of fundamentally new drugs. [ABSTRACT FROM AUTHOR]

The unicellular green alga Chlamydomonas reinhardtii is a model organism for studying energetic metabolism. Most mitochondrial respiratory-deficient mutants characterized to date have been isolated on the basis of their reduced ability to grow in heterotrophic conditions. Mitochondrial deficiencies are usually partly compensated by adjustment of photosynthetic activity and more particularly by transition to state 2. In this work, we explored the opportunity to select mutants impaired in respiration and/or altered in dark metabolism by measuring maximum photosynthetic efficiency by chlorophyll fluorescence analyses ( F V / F M ). Out of about 2900 hygromycin-resistant insertional mutants generated from wild type or from a mutant strain deficient in state transitions ( stt7 strain), 22 were found to grow slowly in heterotrophic conditions and 8 of them also showed a lower F V / F M value. Several disrupted coding sequences were identified, including genes coding for three different subunits of respiratory-chain complex I (NUO9, NUOA9, NUOP4) or for isocitrate lyase (ICL1). Overall, the comparison of respiratory mutants obtained in wild-type or stt7 genetic backgrounds indicated that the F V / F M value can be used to isolate mutants severely impaired in dark metabolism. [ABSTRACT FROM AUTHOR]

Background: The V-ATPase is a proton pump that creates an acidic medium, necessary for lysosome function and vesicular traffic. It is also essential for several developmental processes. Many enzymes, like the V-ATPase, are assemblies of multiple subunits, in which each one performs a specific function required to achieve full activity. In the zebrafish V-ATPase 15 different subunits form this multimeric complex and mutations in any of these subunits induce hypopigmentation or pigment dilution phenotype. We have previously found variability in the pigment dilution phenotype among five of the V-ATPase zebrafish mutants. This work presents additional information about such differences and is an update from a previous report. Findings: We describe the variable phenotype severity observed among zebrafish V-ATPase pigment dilution mutants studying mRNA expression levels from their corresponding genes. At the same time we carried out phylogenetic analysis for this genes. Conclusions: Based in the similarities between different pigment dilution mutants we suggest that there is an essential role for V-ATPases in melanosome biogenesis and melanocyte survival. Neither variable expression levels for the different V-ATPase subunits studied here or the presence of duplicated genes seems to account for the variable phenotype severity from this group of mutants. We believe there are some similarities between the pigment dilution phenotype from zebrafish V-ATPase insertional mutants and pigment mutants obtained in a chemical screening ("Tubingen pigmentation mutants"). As for some of these "Tubingen mutants" the mutated gene has not been found we suggest that mutations in V-ATPase genes may be inducing their defects. [ABSTRACT FROM AUTHOR]

Bulk Segregant Analysis (BSA) was used to identify SSR markers associated with polyembryonic (OsPE), gibberellic acid insensitive dwarf (OsGAI/Sd), and oligoculm (Osoc) T-DNA insertional mutants of Basmati 370. Mapping populations were developed by crossing insertional mutants with non-basmati rice cultivar PR106. Southern hybridization in the mutants using the hpt probe confirmed single copy T-DNA insertions. The segregation ratios for germination on hygromycin and PCR amplification of hpt of different mutant populations had a good fit to 3:1 ratio confirming the single copy T-DNA insertions. The mutant phenotypes also cosegregated with the hpt gene indicating that they were due to T-DNA insertions. A set of 98 SSR markers showing polymorphism between parental lines was used for identifying markers associated with the OsPE, OsGAI/Sd, and Osoc loci through BSA. Two flanking markers RM14645 and RM14667 on chromosome 3 were linked to OsPE (5.79 cM and 2.17cM) and OsGAI/Sd (1.21cM and 6.49cM), respectively. Osoc was linked with RM279 (6.73cM), RM236 (2.45cM), and RM12413 (1.47cM) on chromosome 2. The work to clone the candidate genes for OsPE, OsGAI/Sd and Osoc in the three independent T-DNA insertional mutants is in progress. [ABSTRACT FROM AUTHOR]

To improve the analysis of unknown flanking DNA sequences adjacent to known sequences in nuclear genomes of photoautotrophic eukaryotic organisms, we established the technique of ligation-mediated suppression-PCR (LMS-PCR) in the green alga Chlamydomonas reinhardtii for (1) walking from a specific nuclear insertion fragment of random knockout mutants into the unknown flanking DNA sequence to identify and analyse disrupted genomic DNA regions and for (2) walking from highly conserved DNA regions derived from known gene iso-forms into flanking DNA sequences to identify new members of protein families. The feasibility of LMS-PCR for these applications was successfully demonstrated in two different approaches. The first resulted in the identification of a genomic DNA fragment flanking a nuclear insertion vector in a random knockout mutant whose phenotype was characterised by its inability to perform functional LHC state transitions. The second approach targeted the cab gene family. An oligonucleotide of a cabII gene, derived from a highly conserved region, was used to identify potential cab gene regions in the nuclear genome of Chlamydomonas. LMS-PCR combined with 3′ rapid amplification of cDNA ends (3′ RACE) and a PCR-based screening of a cDNA library resulted in the identification of the new cabII gene lhcb4. Both results clearly indicate that LMS-PCR is a powerful tool for the identification of flanking DNA sequences in the nuclear genome of Chlamydomonas reinhardtii. [ABSTRACT FROM AUTHOR]

Abstract A method was developed to identify insertional mutants of Chlamydomonas reinhardtii disrupted for selected target genes. The approach relies on the generation of thousands of transformants followed by PCR-based screenings that allow for identification of strains harboring the introduced marker gene within specific genes of interest. Our results highlight the strengths and limitations of two independent screens that differed in the nature of the marker DNA used (PCR-amplified fragment containing the plasmid-free marker versus entire linearized plasmid with the marker) and in the strategies used to maintain and store transformants.