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Key Message: SpG Cas9 significantly expands the genome editing scope in carrot with NGN PAM recognition., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Phytohormones play an important role in the pollination and fertilization of crops, but the regulatory mechanisms of oil palm pollination and fertilization are unclear. The purpose of this study is to explore the hormonal changes of oil palm pistils during flowering. We used RNA sequencing to evaluate differentially expressed genes (DEGs) in oil palm pistils at the pollination and non-pollination stages. In this study, we found that the hormone contents of oil palm pistil changed drastically after pollination. The transcriptome of the oil palm pistil without pollination and at 2 h, 4 h, 12 h, 24 h, and 48 h after pollination was comprehensively analyzed, and a large number of differential genes and metabolic pathways were explored. Based on the transcriptome data, it could be recognized that the changes of indoleacetic acid (IAA), zeatin riboside (ZR), and abscisic acid (ABA) during pollination were consistent with the changes in the corresponding gene transcripts. Differentially expressed genes during pollination and fertilization of oil palm were mainly related to energy metabolism and hormone signal transduction. It provides new insights to elucidate the interaction and regulation mechanisms of plant hormones before and after oil palm pollination, providing a theoretical basis and reference for the research on sexual reproduction of oil palm., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The bZIP transcription factors are well-known transcription regulators and play a key role in regulating various developmental, biological processes, and stress responses in plants. However, information on bZIP transcription factors is not yet available in oil palm, an important oil yielding crop. The present study identified the 97 bZIP transcription factor family members in oil palm genome via a genome-wide approach. Phylogenetic analysis clustered all EgbZIPs into 12 clusters with Arabidopsis and rice bZIPs. EgbZIP gene structure analysis showed a distinct variation in the intron-exon organization among all EgbZIPs. Conserved motif analysis demonstrated the occurrence of ten additional conserved motifs besides having a common bZIP domain. All the identified 97 EgbZIPs were unevenly distributed on 16 chromosomes and exhibited tandem duplication in oil palm genome. Our results aslo demonstrated that tissue-specific expression patterns of EgbZIPs based on the available transcriptome data of six different tissue of oil palm. Stress-responsive expression analysis showed that 11EgbZIP transcription factors were highly expressed under cold, salinity, drought stress conditions. Taken together, our findings will provide insightful information on bZIP transcription factors as one of the stress-responsive regulators in oil palm., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Key Message: We found that overexpression of EgMYB111 and EgMYB157 genes positively regulate the abiotic stress tolerance. MYB family genes are well-known regulators in modulating the abiotic stress-responsive mechanisms in plants. However, lesser is known about the functional roles of oil palm MYB genes. Previously, we found that oil palm MYB genes such as EgMYB111 and EgMYB157 were significantly up-regulated under salinity, cold, and drought stress conditions. In this study, we over-expressed EgMYB111 and EgMYB157 genes separately in Arabidopsis plants. The transgenic Arabidopsis plants expressing EgMYB111 have shown improved tolerance to salinity, cold and drought stress conditions, whereas transgenic Arabidopsis plants expressing EgMYB157 dispalyed improved tolerance to cold and drought stress conditions only. Various biochemical analyses also revealed significant improvement of antioxidant enzyme activities, photosynthetic pigments, net photosynthetic rate, stomatal conductance, and intercellular CO2 concentration in transgenic plants compared to wild-type plants under cold, drought, and salinity stress conditions. Significant up-regulation of various known stress marker genes such as RD22, RD29A, RAB18, COR47, ABA1, ABI1, HAB1 was also noticed in EgMYB111 and EgMYB157 expressing transgenic plants compared to wild-type plants under cold, drought, and salinity stress conditions. Taken together, over-expression of EgMYB111 and/or EgMYB157 significantly improve abiotic tolerance in transgenic Arabidopsis plants, indicating that EgMYB111 and EgMYB157 are the potential candidates for developing abiotic stress-tolerant crops in near future., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Auxin response factors (ARFs) play vital role in controlling growth and developmental processes of plants via regulating the auxin signaling pathways. However, the identification and functional roles of ARFs in oil palm plants remain elusive. Here, we identified a total of 23 ARF (EgARF) genes in oil palm through a genome-wide identification approach. The EgARF gene structure analysis revealed the presence of intron-rich ARF gene family in genome of oil palm. Further analysis demonstrated the uneven distribution of 23EgARFs on 16 chromosomes of oil palm. Phylogenetic analysis clustered all the EgARFs into four groups. Twenty-one EgARFs contained BDD, ARF, and CTD domains, whereas EgARF5 and EgARF7 lacked the CTD domain. The evolution of ARF genes in oil palm genome has been expanded by segmental duplication events. The cis-acting regulatory elements of EgARF gene family were predominantly associated with the stress and hormone responses. Expression profiling data demonstrated the constitutive and tissue-specific expression of EgARF genes in various tissues of oil palm. Real-time PCR analysis of 19 EgARF genes expression levels under cold, drought, and salt stress conditions proved their prominent role under abiotic stress responses. Altogether, our study provides a basis for studying the molecular and functional roles of ARF genes in oil palm., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

NAC-type transcription factors are crucial players in the abiotic stress responses of plants. Soybean NAC-type transcription factor GmNAC20 was transformed into rice genome via Agrobacterium method of transformation to improve abiotic stress tolerance. Integration and expression of GmNAC20 were verified by the DNA blot hybridization, immunoblotting, RT-PCR, and quantitative RT-PCR in T 3 generation of transgenic rice plants. Significant expression of GmNAC20 was found in transgenic plants under salinity, cold, and IAA treatments. The transgenic rice plants expressing GmNAC20 displayed enhanced salinity and cold stress tolerance via upregulating the abiotic stress-responsive genes. Furthermore, T 3 transgenic plants retained relative water content, chlorophyll content with enhanced accumulation of proline content than wild-type plants under salinity, and cold stress environments. The decrease in MDA content and electrolyte leakage with a significant increase in antioxidant enzyme activities were noticed in transgenic rice plants under either salinity or cold stress conditions, compared to wild-type plants. Overexpression of GmNAC20 in rice plants also induced the lateral root formation, associated with upregulation of auxin signaling-related genes. Taken together, our results indicated that GmNAC20 acts as a positive regulator for conferring salinity and cold tolerance in rice plants and appropriate candidate for improving salinity and cold stress in other important food crops., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Key Message: Base editing is one of the promising genome editing tools for generating single-nucleotide changes in rice genome. Rice (Oryza sativa L.) is an important staple food crop, feeding half of the population around the globe. Developing new rice varieties with desirable agronomic traits is necessary for sustaining global food security. The use of genome editing technologies for developing rice varieties is pre-requisite in the present scenario. Among the genome editing technologies developed for rice crop improvement, base editing technology has emerged as an efficient and reliable tool for precise genome editing in rice plants. Base editing technology utilizes either adenosine or cytidine base editor for precise editing at the target region. A base editor (adenosine or cytidine) is a fusion of catalytically inactive CRISPR/Cas9 domain and adenosine or cytidine deaminase domain. In this review, authors have discussed the different adenine and cytosine base editors developed so far for precise genome editing of rice via base editing technology. We address the current progress, advances, limitations, as well as future perspectives of the base editing technology for rice crop improvement.

Iron is a critical micronutrient for growth and development of plants and its deficiency limiting the crop productivity. MicroRNAs (miRNAs) play vital roles in adaptation of plants to various nutrient deficiencies. However, the role of miRNAs and their target genes related to Fe-deficiency is limited. In this study, we identified Fe-deficiency-responsive miRNAs from citrus. In Fe-deficiency conditions, about 50 and 31 miRNAs were up-regulated and down-regulated, respectively. The differently expressed miRNAs might play critical roles in contributing the Fe-deficiency tolerance in citrus plants. The miRNAs-mediated Fe-deficiency tolerance in citrus plants might related to the enhanced stress tolerance by decreased expression of miR172; regulation of S homeostasis by decreased expression of miR395; inhibition of plant growth by increased expression of miR319 and miR477; regulation of Cu homeostasis as well as activation of Cu/Zn superoxide dismutase activity due to decreased expression of miR398 and miR408 and regulation of lignin accumulation by decreased expression of miR397 and miR408. The identified miRNAs in present study laid a foundation to understand the Fe-deficiency adaptive mechanisms in citrus plants., Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-021-02669-z., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© King Abdulaziz City for Science and Technology 2021.)

Key Message: The DEAD-Box RNA helicase OsTOGR1 positively regulates heat stress tolerance in Chinese cabbage. Non-heading Chinese cabbage (Brassica rapa L. ssp. chinensis) is primarily cultivated vegetable crop in Asian countries. Heat stress is one of the major threats for its growth and yield. Numerous regulatory genes in various crops have shown to contribute thermotolerance. Among them, Thermotolerant growth required 1 (TOGR1) is an important DEAD-box RNA helicase. To examine whether its role is conserved in other crops, we constructed pCAMBIA1300-pHSP:OsTOGR1 expression vector driven by the rice small heat shock protein promoter (pHSP17.9) and successfully produced transgenic non-heading Chinese cabbage plants expressing OsTOGR1 gene via Agrobacterium-mediated vacuum infiltration transformation. In total, we generated three independent transgenic cabbage lines expressing TOGR1 gene. Expression and integration of TOGR1 was confirmed by PCR, RT-PCR and qPCR in T 1 and T 2 generations. The relative leaf electrical conductivity of transgenic seedlings was reduced subjected to high temperature (38 °C) compared to heat shock treatment (46 °C). In addition, hypocotyl length of transgenic seedlings increased compared to wild-type plants under high temperature and heat shock treatment. Furthermore, the transgenic plants exhibited higher chlorophyll content than wild-type plants under high temperature and heat shock treatment. The transgenic seeds displayed better germination under heat shock treatment. Tested heat stress-responsive genes were also up-regulated in the transgenic plants subjected to high temperature or heat shock treatment. To the best of our knowledge, this is the first report on describing the role of DAED-Box RNA helicases in improving heat stress tolerance of transgenic plants.

Somatic embryogenesis is the regeneration of embryos from the somatic cell via dedifferentiation and redifferentiation without the occurrence of fertilization. A complex network of genes regulates the somatic embryogenesis process. Especially, microRNAs (miRNAs) have emerged as key regulators by affecting phytohormone biosynthesis, transport and signal transduction pathways. miRNAs are small, non-coding small RNA regulatory molecules involved in various developmental processes including somatic embryogenesis. Several types of miRNAs such as miR156, miR157, miR 159, miR 160, miR165, miR166, miR167, miR390, miR393 and miR396 have been reported to intricate in regulating somatic embryogenesis via targeting the phytohormone signaling pathways. Here we review current research progress on the miRNA-mediated regulation involved in somatic embryogenesis via regulating auxin, ethylene, abscisic acid and cytokinin signaling pathways. Further, we also discussed the possible role of other phytohormone signaling pathways such as gibberellins, jasmonates, nitric oxide, polyamines and brassinosteroids. Finally, we conclude by discussing the expression of miRNAs and their targets involved in somatic embryogenesis and possible regulatory mechanisms cross talk with phytohormones during somatic embryogenesis., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© King Abdulaziz City for Science and Technology 2020.)

The improvement of the yield and quality of oil palm via precise genome editing has been indispensable goal for oil palm breeders. Genome editing via the CRISPR/Cas9 (CRISPR-associated protein 9) system, ZFN (zinc finger nucleases) and TALEN (transcription activator-like effector nucleases) has flourished as an efficient technology for precise target modifications in the genomes of various crops. Among the genome editing technologies, base editing approach has emerged as novel technology that could generate single base changes i.e. irreversible conversion of one target base in to other in a programmable manner. A base editor (adenine or cytosine) is a fusion of catalytically inactive CRISPR-Cas9 domain (Cas9 variants) and cytosine or adenosine deaminase domain that introduces desired point mutations. However, till date no such genetic modifications have ever been developed in oil palm via base editing technology. Precise genome editing via base editing approach can be a challenging task in oil palm due to its complex genome as well as difficulties in tissue culture and genetic transformation methods. However, availability of whole genome sequencing data in oil palm provides a platform for developing the base editing technology. Here, we briefly review the potential application and future implications of base editing technology for the genetic improvement of oil palm., Competing Interests: Conflict of interestThe authors declare no conflict of interest., (© King Abdulaziz City for Science and Technology 2020.)

Present study mainly aimed to ascertain the distribution characteristics of gene-based microsatellite loci and to develop polymorphic SSR markers from the already available transcriptome data of Elaeis guineensis Jacq, an important oil crop. From this study, we identified the sum of 5791 SSRs across 51,425 unigenes from the transcripts of oil palm. We were able to evaluate 331primer pairs and characterized 183 polymorphic gene-based SSR markers. We identified a total of 506 alleles from the 183 polymorphic SSR loci, with an average of 2.77 alleles per locus. The characterized gene-based SSR markers from the transcriptome data of oil palm exhibited moderate levels of polymorphism with a significant level of heterozygosity ranges from 0.096 to 0.594 (mean = 0.336 ± 0.11). Among the identified SSR markers, sixty polymorphic markers were used to analyze genotypes of 55 oil palm accessions selected from three different provinces of China. Association mapping analysis provided the information of four markers that are associated with fruit shell thickness trait of oil palm. Among the four markers identified from association analysis, one SSR marker obtained from Unigene17150 is strictly associated with the oil palm fruit shell thickness trait., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© King Abdulaziz City for Science and Technology 2020.)

Brinjal or eggplant (Solanum melongena L.) is an important solanaceous edible crop, and salt stress adversely affects its growth, development, and overall productivity. To cope with excess salinity, vacuolar Na + /H + antiporters provide the best mechanism for ionic homeostasis in plants under salt stress. We generated transgenic eggplants by introducing wheat TaNHX2 gene that encodes a vacuolar Na + /H + antiporter in to the eggplant genome via Agrobacterium-mediated transformation using pBin438 vector that harbors double35S:TaNHX2 to confer salinity tolerance. Polymerase chain reaction and southern hybridization confirmed the presence and integration of TaNHX2 gene in T 1 transgenic plants. Southern positive transgenic eggplants showed varied levels of TaNHX2 transcripts as evident by RT-PCR and qRT-PCR. Stress-inducible expression of TaNHX2 significantly improved growth performance and Na + and K + contents from leaf and roots tissues of T 2 transgenic eggplants under salt stress, compared to non-transformed plants. Furthermore, T 2 transgenic eggplants displayed the stable leaf relative water content and chlorophyll content, proline accumulation, improved photosynthetic efficiency, transpiration rate, and stomatal conductivity than the non-transformed plants under salinity stress (200 mM NaCl). Data showed that the T 2 transgenic lines revealed that reduction in MDA content, hydrogen peroxide, and oxygen radical production associated with the significant increase of antioxidant enzyme activity in transgenic eggplants than non-transformed plants under salt stress (200 mM NaCl). This study suggested that the TaNHX2 gene plays an important regulatory role in conferring salinity tolerance of transgenic eggplant and thus may serve as a useful candidate gene for improving salinity tolerance in other vegetable crops.