HD-Zip proteins modify floral structures for self-pollination in tomato.

Cleistogamy is a type of self-pollination that relies on the formation of a stigma-enclosing floral structure. We identify three homeodomain-leucine zipper IV (HD-Zip IV) genes that coordinately promote the formation of interlocking trichomes at the anther margin to unite neighboring anthers, generating a closed anther cone and cleistogamy (flower morphology necessitating strict self-pollination). These HD-Zip IV genes also control style length by regulating the transition from cell division to endoreduplication. The expression of these HD-Zip IV genes and their downstream gene, Style 2.1, was sequentially modified to shape the cleistogamy morphology during tomato evolution and domestication. Our results provide insights into the molecular basis of cleistogamy in modern tomato and suggest targets for improving fruit set and preventing pollen contamination in genetically modified crops.

Overexpression of transcription factor FaMYB63 enhances salt tolerance by directly binding to the SOS1 promoter in Arabidopsis thaliana.

Salinity is a pivotal abiotic stress factor with far-reaching consequences on global crop growth, yield, and quality and which includes strawberries. R2R3-MYB transcription factors encompass a range of roles in plant development and responses to abiotic stress. In this study, we identified that strawberry transcription factor FaMYB63 exhibited a significant upregulation in its expression under salt stress conditions. An analysis using yeast assay demonstrated that FaMYB63 exhibited the ability to activate transcriptional activity. Compared with those in the wild-type (WT) plants, the seed germination rate, root length, contents of chlorophyll and proline, and antioxidant activities (SOD, CAT, and POD) were significantly higher in FaMYB63-overexpressing Arabidopsis plants exposed to salt stress. Conversely, the levels of malondialdehyde (MDA) were considerably lower. Additionally, the FaMYB63-overexpressed Arabidopsis plants displayed a substantially improved capacity to scavenge active oxygen. Furthermore, the activation of stress-related genes by FaMYB63 bolstered the tolerance of transgenic Arabidopsis to salt stress. It was also established that FaMYB63 binds directly to the promoter of the salt overly sensitive gene SOS1, thereby activating its expression. These findings identified FaMYB63 as a possible and important regulator of salt stress tolerance in strawberries.

Overexpression of PvWAK3 from seashore paspalum increases salt tolerance in transgenic Arabidopsis via maintenance of ion and ROS homeostasis.

Seashore paspalum (Paspalum vaginatum O. Swartz) is an important warm-season turfgrass species with extreme salt tolerance, but investigations on its salt tolerance mechanism are limited. A salt induced PvWAK3 from halophyte seashore paspalum was identified in this study. Overexpression of PvWAK3 in Arabidopsis led to increased salt tolerance. Transgenic plants had higher levels of seed germination rate, root length, number of lateral roots, shoot weight, survival rate, Fv/Fm, ETR, and NPQ compared with the wild type (WT) under salt stress. Na+ content was increased and K+ content was decreased after salinity treatment, with lower levels of Na+ and Na+/K+ ratio but higher level of K+ in transgenic plants than in WT under salt stress. The improved maintenance of Na+ and K+ homeostasis was associated with the higher transcript levels of K + -Uptake Permease 4 (KUP4), Potassium Transport 2/3 (AKT2), Salt Overly Sensitive 1 (SOS1) and High-Affinity K + Transporter 5 (HAK5) in transgenic plants compared with WT. Superoxide dismutase (SOD), catalase (CAT) and ascorbate-peroxidase (APX) activities, proline concentration, and P5CS1 transcript were increased after salinity treatment, with higher levels in transgenic lines compared with WT, which led to reduced accumulation of O2·- and H2O2 under salt stress. It is suggested that PvWAK3 regulates salt tolerance positively, which is associated with promoted Na+ and K+ homeostasis, activated antioxidant enzymes, and proline biosynthesis under salt stress.

Kinetics of glyphosate and aminomethylphosphonic acid sorption onto montmorillonite clays in soil and their translocation to genetically modified corn.

The co-occurrence of glyphosate (GLP) and aminomethylphosphonic acid (AMPA) in contaminated water, soil, sediment and plants is a cause for concern due to potential threats to the ecosystem and human health. A major route of exposure is through contact with contaminated soil and consumption of crops containing GLP and AMPA residues. However, clay-based sorption strategies for mixtures of GLP and AMPA in soil, plants and garden produce have been very limited. In this study, in vitro soil and in vivo genetically modified corn models were used to establish the proof of concept that the inclusion of clay sorbents in contaminated soils will reduce the bioavailability of GLP and AMPA in soils and their adverse effects on plant growth. Effects of chemical concentration (1-10 mg/kg), sorbent dose (0.5%-3% in soil and 0.5%-1% in plants) and duration (up to 28 days) on sorption kinetics were studied. The time course results showed a continuous GLP degradation to AMPA. The inclusion of calcium montmorillonite (CM) and acid processed montmorillonite (APM) clays at all doses significantly and consistently reduced the bioavailability of both chemicals from soils to plant roots and leaves in a dose- and time-dependent manner without detectable dissociation. Plants treated with 0.5% and 1% APM inclusion showed the highest growth rate (p ≤ 0.05) and lowest chemical bioavailability with up to 76% reduction in roots and 57% reduction in leaves. Results indicated that montmorillonite clays could be added as soil supplements to reduce hazardous mixtures of GLP and AMPA in soils and plants.

Knockdown of Sly-miR164a Enhanced Plant Salt Tolerance and Improved Preharvest and Postharvest Fruit Nutrition of Tomato.

Salinity stress is a serious limitation to tomato growth and development. The aim of this study was to investigate the effects of Sly-miR164a on tomato growth and fruit nutritional quality under salt stress. The results showed that the root length, fresh weight, plant height, stem diameter and ABA content of miR164a#STTM (knockdown of Sly-miR164a) lines were higher than those of WT and miR164a#OE (overexpression of Sly-miR164a) lines under salt stress. Compared with WT, miR164a#STTM tomato lines exhibited lower ROS accumulation under salt stress. In addition, the fruits of miR164a#STTM tomato lines had higher soluble solids, lycopene, ascorbic acid (ASA) and carotenoid content compared with WT. The study indicated that tomato plants were more sensitive to salt when Sly-miR164a was overexpressed, while knockdown of Sly-miR164a enhanced plant salt tolerance and improved fruit nutritional value.

Overexpression of a plant U-box gene TaPUB4 confers drought stress tolerance in Arabidopsis thaliana.

Drought stress frequently results in significant reductions in crop production and yield. Plant U-box proteins (PUB) play a key role in the response to abiotic stress. Despite extensive characterization of PUB in model plants, their roles in wheat abiotic stress response remains unknown. In this study, we identified the physiological function of TaPUB4, a gene encoding the U-box and nuclear localization domains. The transcription level of TaPUB4 was induced by drought (mannitol) and abscisic acid. TaPUB4 displays E3 ubiquitin ligase activity and is located in the nucleus. Overexpression of TaPUB4 in Arabidopsis plants enhanced sensitivity with under ABA condition during early seedling developmental stages. In addition, the stomatal conductance of TaPUB4 was closer to that of WT under ABA conditions. Moreover, TaPUB4 facilitated stomatal response to elevated CO2 emission rates under ABA conditions. TaPUB4-overexpressing Arabidopsis, on the other hand, was more resistant to drought stress in plant development, demonstrating that TaPUB4 positively regulates drought-mediated control of plant growth. Moreover, the ectopic expression of the TaPUB4 gene was significant influential in drought sensitive metrics including survival rate, chlorophyll content, water loss, proline content and the expression of drought stress-response genes. Collectively, our results demonstrate that TaPUB4 may regulate drought stress response and ABA conditions.

Transgenerational Tolerance to Salt and Osmotic Stresses Induced by Plant Virus Infection.

Following pathogen infection, plants have developed diverse mechanisms that direct their immune systems towards more robust induction of defense responses against recurrent environmental stresses. The induced resistances could be inherited by the progenies, rendering them more tolerant to stressful events. Although within-generational induction of tolerance to abiotic stress is a well-documented phenomenon in virus-infected plants, the transgenerational inheritance of tolerance to abiotic stresses in their progenies has not been explored. Here, we show that infection of Nicotiana benthamiana plants by Potato virus X (PVX) and by a chimeric Plum pox virus (PPV) expressing the P25 pathogenicity protein of PVX (PPV-P25), but not by PPV, conferred tolerance to both salt and osmotic stresses to the progeny, which correlated with the level of virulence of the pathogen. This transgenerational tolerance to abiotic stresses in the progeny was partially sustained even if the plants experience a virus-free generation. Moreover, progenies from a Dicer-like3 mutant mimicked the enhanced tolerance to abiotic stress observed in progenies of PVX-infected wild-type plants. This phenotype was shown irrespective of whether Dicer-like3 parents were infected, suggesting the involvement of 24-nt small interfering RNAs in the transgenerational tolerance to abiotic stress induced by virus infection. RNAseq analysis supported the upregulation of genes related to protein folding and response to stress in the progeny of PVX-infected plants. From an environmental point of view, the significance of virus-induced transgenerational tolerance to abiotic stress could be questionable, as its induction was offset by major reproductive costs arising from a detrimental effect on seed production.

Overexpression of PgCBF3 and PgCBF7 Transcription Factors from Pomegranate Enhances Freezing Tolerance in Arabidopsis under the Promoter Activity Positively Regulated by PgICE1.

Cold stress limits plant growth, development and yields, and the C-repeat binding factors (CBFs) function in the cold resistance in plants. However, how pomegranate CBF transcription factors respond to cold signal remains unclear. Considering the significantly up-regulated expression of PgCBF3 and PgCBF7 in cold-tolerant Punica granatum 'Yudazi' in comparison with cold-sensitive 'Tunisia' under 4 °C, the present study focused on the two CBF genes. PgCBF3 was localized in the nucleus, while PgCBF7 was localized in the cell membrane, cytoplasm, and nucleus, both owning transcriptional activation activity in yeast. Yeast one-hybrid and dual-luciferase reporter assay further confirmed that PgICE1 could specifically bind to and significantly enhance the activation activity of the promoters of PgCBF3 and PgCBF7. Compared with the wild-type plants, the PgCBF3 and PgCBF7 transgenic Arabidopsis thaliana lines had the higher survival rate after cold treatment; exhibited increased the contents of soluble sugar and proline, while lower electrolyte leakage, malondialdehyde content, and reactive oxygen species production, accompanying with elevated enzyme activity of catalase, peroxidase, and superoxide dismutase; and upregulated the expression of AtCOR15A, AtCOR47, AtRD29A, and AtKIN1. Collectively, PgCBFs were positively regulated by the upstream PgICE1 and mediated the downstream COR genes expression, thereby enhancing freezing tolerance.

The long-term persistence of transgenic volunteers in wild mustard and rice populations.

The undesired presence of GM plants outside of cultivation is one of main concerns for the ecological risk assessment and regulation of GM plants, and how long transgenic volunteers can persist in the nature remains unknown. We conducted two long-term coexistence experiments of Bt-transgenic insect-resistant crops in populations of their wild relatives, using Bt-transgenic oilseed rape (Brassica napus) in wild mustard (B. juncea) populations from 2012 to 2019, and Bt-transgenic rice (Oryza sativa) in wild rice (O. rufipogon and O. minuta) populations from 2013 to 2019. Transgenic oilseed rape volunteers survived only in the 2012 winter, because it is a spring variety and not be resistant to cold climate and competition from weeds. Transgenic rice was not survived because of its low competitive ability compared to wild rice, but survived five years in one population of wild rice O. minuta who could not tolerant to cold temperature. Our results indicated that transgenic volunteers can persist in the wild populations under natural conditions, but the fate of transgenic volunteers in the nature depends on whether the growth environment is favorable, and they could not disperse over its niche or "tolerance zone".

GsERF1 enhances Arabidopsis thaliana aluminum tolerance through an ethylene-mediated pathway.

Ethylene response factor (ERF) transcription factors constitute a subfamily of the AP2/ERF superfamily in plants and play multiple roles in plant growth and development as well as in stress responses. In this study, the GsERF1 gene from the wild soybean BW69 line (an Al-resistant Glycine soja line) was rapidly induced in response to aluminum stress. Quantitative real-time PCR (qRT-PCR) analysis showed that the GsERF1 gene maintained a constitutive expression pattern and was induced in soybean in response to aluminum stress, with increased amounts of transcripts detected in the roots. The putative GsERF1 protein, which contains an AP2 domain, was located in the nucleus and maintained transactivation activity. In addition, under AlCl3 treatment, GsERF1 overexpression increased the relative growth rate of the roots of Arabidopsis and weakened the hematoxylin staining of hairy roots. Ethylene synthesis-related genes such as ACS4, ACS5 and ACS6 were upregulated in GsERF1 transgenic lines compared with the wild type under AlCl3 treatment. Furthermore, the expression levels of stress/ABA-responsive marker genes, including ABI1, ABI2, ABI4, ABI5 and RD29B, in the GsERF1 transgenic lines were affected by AlCl3 treatment, unlike those in the wild type. Taken together, the results indicated that overexpression of GsERF1 may enhance aluminum tolerance of Arabidopsis through an ethylene-mediated pathway and/or ABA signaling pathway, the findings of which lay a foundation for breeding soybean plants tolerant to aluminum stress.

Overexpression of the Salix matsudana SmAP2-17 gene improves Arabidopsis salinity tolerance by enhancing the expression of SOS3 and ABI5.

BACKGROUND: Salix matsudana (Koidz.) is a widely planted ornamental allotetraploid tree species. Genetic engineering can be used to enhance the tolerance of this species to soil salinization, endowing varieties with the ability to grow along coastlines, thereby mitigating afforestation and protecting the environment. The AP2/ERF family of transcription factors (TFs) plays multidimensional roles in plant biotic/abiotic stress tolerance and plant development. In this study, we cloned the SmAP2-17 gene and performed functional analysis of its role in salt tolerance. This study aims to identify key genes for future breeding of stress-resistant varieties of Salix matsudana. RESULTS: SmAP2-17 was predicted to be a homolog of AP2-like ethylene-responsive transcription factor ANT isoform X2 from Arabidopsis, with a predicted ORF of 2058 bp encoding an estimated protein of 685 amino acids containing two conserved AP2 domains (PF00847.20). SmAP2-17 had a constitutive expression pattern and was localized to the nucleus. The overexpression of the native SmAP2-17 CDS sequence in Arabidopsis did not increase salt tolerance because of the reduced expression level of ectopic SmAP2-17, potentially caused by salt-induced RNAi. Transgenic lines with high expression of optimized SmAP2-17 CDS under salt stress showed enhanced tolerance to salt. Moreover, the expression of general stress marker genes and important salt stress signaling genes, including RD29A, ABI5, SOS3, AtHKT1, and RBohF, were upregulated in SmAP2-17-overexpressed lines, with expression levels consistent with that of SmAP2-17 or optimized SmAP2-17. Promoter activity analysis using dual luciferase analysis showed that SmAP2-17 could bind the promoters of SOS3 and ABI5 to activate their expression, which plays a key role in regulating salt tolerance. CONCLUSIONS: The SmAP2-17 gene isolated from Salix matsudana (Koidz.) is a positive regulator that improves the resistance of transgenic plants to salt stress by upregulating SOS3 and ABI5 genes. This study provides a potential functional gene resource for future generation of salt-resistant Salix lines by genetic engineering.

Wheat TaTIP4;1 Confers Enhanced Tolerance to Drought, Salt and Osmotic Stress in Arabidopsis and Rice.

Tonoplast aquaporins (intrinsic proteins, TIPs) have been indicated to play important roles in plant tolerance to water deficit and salinity. However, the functions of wheat TIPs in response to the stresses are largely unknown. In this study, we observed that transgenic plants overexpressing wheat TaTIP4;1 in Arabidopsis and rice displayed clearly enhanced seed germination and seedling growth under drought, salt and osmotic stress. Compared with wild type plants, Arabidopsis and rice overexpression lines had heightened water contents, reduced leaf water loss, lowered levels of Na+, Na+/K+, H2O2 and malondialdehyde, and improved activities of catalase and/or superoxide dismutase, and increased accumulation of proline under drought, salinity and/or osmotic stresses. Moreover, the expression levels of multiple drought responsive genes clearly elevated upon water dehydration, and the transcription of some salt responsive genes was markedly induced by NaCl treatment in the overexpression lines. Also, the yeast cells containing TaTIP4;1 showed increased tolerance to NaCl and mannitol, and mutation in one of three serines of TaTIP4;1 caused decreased tolerance to the two stresses. These results suggest that TaTIP4;1 serves as an essential positive regulator of seed germination and seedling growth under drought, salt and/or osmotic stress through impacting water relations, ROS balance, the accumulation of Na+ and proline, and stimulating the expression of dozens of stress responsive genes in Arabidopsis and rice. Phosphorylation may modulate the activity of TaTIP4;1.

Isolation and functional analysis of two CONSTANS-like 1 genes from mango.

The CONSTANS-LIKE1 (COL1) gene plays an important role in the regulation of photoperiodic flowering in plants. In this study, two COL1 homolog genes, MiCOL1A and MiCOL1B, were isolated from mango (Mangifera indica L.). The open reading frames of MiCOL1A and MiCOL1B are 852 and 822 bp in length and encode 284 and 274 amino acids, respectively. The MiCOL1A and MiCOL1B proteins contain only one CCT domain and belong to the CO/COL group IV protein family. MiCOL1A and MiCOL1B were expressed both in vegetative and reproductive organs but with expression level differences. MiCOL1A was highly expressed in juvenile and adult leaves, but MiCOL1B was highly expressed in flowers. Seasonal expression analysis showed that MiCOL1A and MiCOL1B have similar expression patterns and higher expression levels during flower induction and flower organ differentiation periods. However, MiCOL1A and MiCOL1B exhibited unstable patterns in circadian expression analysis. MiCOL1A and MiCOL1B were localized in the nucleus and had transcriptional activation activity in yeast. Overexpression of MiCOL1A and MiCOL1B resulted in significantly delayed flowering time in Arabidopsis. Furthermore, we also found that overexpression of MiCOL1A and MiCOL1B enhanced drought tolerance in transgenic Arabidopsis. The results demonstrated that MiCOL1A and MiCOL1B are not only involved in flowering regulation but also play a role in the stress response of plants.

Overexpression of the Selaginella lepidophylla bHLH transcription factor enhances water-use efficiency, growth, and development in Arabidopsis.

Abiotic stresses have the greatest impact on the growth and productivity of crops, especially under current and future extreme weather events due to climate change. Thus, it is vital to explore novel strategies to improve crop plant abiotic stress tolerance to feed an ever-growing world population. Selaginella lepidophylla is a desiccation-tolerant spike moss with specialized adaptations that allow it to tolerate water loss down to 4% relative water content. A candidate basic helix-loop-helix (bHLH) transcription factor was highly expressed at 4% relative water content in S. lepidophylla (SlbHLH). This SlbHLH gene was codon-optimized (SlbHLHopt) and overexpressed in Arabidopsis for functional characterization. Overexpression of the SlbHLHopt gene not only significantly increased plant growth, development, and integrated water-use efficiency, but also significantly increased seed germination and green cotyledon emergence rates under water-deficit stress and salt stress conditions. Under a 150 mM NaCl salt stress condition, SlbHLHopt-overexpressing lines increased primary root length, the number of lateral roots, and fresh and dry biomass at the seedling stage compared to control lines. Interestingly, SlbHLHopt-overexpressing lines also have significantly higher flavonoid content. Altogether, these results suggest that SlbHLH functions as an important regulator of plant growth, development, abiotic stress tolerance, and water-use efficiency.

A bZIP transcription factor VabZIP12 from blueberry induced by dark septate endocyte improving the salt tolerance of transgenic Arabidopsis.

Dark septate endophytes (DSEs) have attracted much attention due to their positive roles in plant growth as well as resistance to various abiotic stresses. However, there are no reports on the molecular mechanisms of DSE fungi to improve salt tolerance in plants. In this study, the blueberry seedlings inoculated with T010, a beneficial DSE fungus reported previously, grew more vigorously than the non-inoculated control under salt stress. Physiological indicators showed that T010 inoculation increased antioxidant activities of blueberry roots. To explore its molecular mechanism, we focused on the bZIP TFs VabZIP12, who was highly up-regulated with T010 inoculation under salt stress. Further studies showed that VabZIP12, as a transcription activator, could combine both G-Box 1 and G-Box 2 motifs. Moreover, overexpression of VabZIP12 enhanced salt stress tolerance through increasing the activities of the enzymatic antioxidants in the transgenic Arabidopsis with up-regulation the related genes. These results indicated that the induction of VabZIP12 contribute to improving the tolerance of blueberry to salt stress by T010 inoculation.

Overexpression of tomato thioredoxin h (SlTrxh) enhances excess nitrate stress tolerance in transgenic tobacco interacting with SlPrx protein.

The thioredoxin (Trx) system plays a vital function in cellular antioxidative defense. However, little is known about Trx in tomato under excess nitrate. In this study, we isolated the tomato gene encoding h-type Trx gene (SlTrxh). The mRNA transcript of SlTrxh in roots and leaves of tomato was induced incrementally under excess nitrate for 24 h. Subcellular localization showed that SlTrxh might localize in the cytoplasm, nucleus and plasma membrane. Enzymatic activity characterization revealed that SlTrxh protein possesses the disulfide reductase function and Cysteine (Cys) 54 is important for its activity. Overexpressing SlTrxh in tobacco resulted in increasing seed germination rate, root length and decreasing H2O2 and O2- accumulation, compared with the wild type (WT) tobacco under nitrate stress. While overexpressing SlTrxhC54S (Cysteine 54 mutated to Serine) in tobacco showed decreased germination rate and root length compared with the WT after nitrate treatment. After nitrate stress treatment, SlTrxh overexpressing transgenic tobacco plants have lower malonaldehyde (MDA), H2O2 contents and Reactive Oxygen Species (ROS) accumulation, and higher mRNA transcript level of NtP5CS, NtDREB2, higher ratio of ASA/DHA and GSH/GSSG, higher activities of ascorbate peroxidase and NADP thioredoxin reductase. Besides, SlTrxh overexpressing plants showed higher tolerance to Methyl Viologen (MV) in the seed germination and seedling stage. The yeast two-hybrid, pull-down, Co-immunoprecipitation and Bimolecular luciferase complementation assay confirmed that SlTrxh physically interacted with tomato peroxiredoxin (SlPrx). These results suggest that SlTrxh contributes to maintaining ROS homeostasis under excess nitrate stress interacting with SlPrx and Cys54 is important for its enzyme activity.

Insight into VvGH3 genes evolutional relationship from monocotyledons and dicotyledons reveals that VvGH3-9 negatively regulates the drought tolerance in transgenic Arabidopsis.

The Gretchen Hagen3 (GH3) gene family is necessary for growth and development in plants and is regulated by osmotic stress and various hormones. Although it has been reported in many plants, the evolutionary relationship of GH3 in grape has not been systematically analyzed from the perspective of monocotyledonous and dicotyledonous. This study identified and analyzed 188 GH3 genes, which were distinctly divided into 9 subgroups, and found these subgroups have obviously been clustered between monocotyledonous and dicotyledonous. VvGH3-x genes had higher synteny with apple and Arabidopsis than that of rice, and the average Ka/Ks value in monocotyledons was higher than that of dicotyledons. The codon usage index showed that monocotyledons preferred to use G3s, C3s, and GC3s, while dicotyledons preferred to use A3s and T3s. The GH3 genes of grape exhibited different expression patterns in various tissues, different abiotic stresses, and hormonal treatments. The subcellular localization showed that VvGH3-9 was expressed in the nucleus and cytoplasm. Additionally, under 20% PEG treatment, the IAA and ABA contents, relative expression levels of VvGH3-9, relative electrical conductivity (REC), as well as MDA were obviously increased in VvGH3-9 overexpression lines at 72 h. In contrast, compared to WT, the contents of proline and H2O2, the activities of POD, SOD, and CAT, and the relative expression levels of drought responsive genes were significantly decreased in overexpressing lines. Collectively, this study provided helpful insight for the evolution of GH3 genes and presented some possibilities to study the functions of GH3 genes in monocotyledons and dicotyledons.

Toward synthetic plant development.

The ability to engineer plant form will enable the production of novel agricultural products designed to tolerate extreme stresses, boost yield, reduce waste, and improve manufacturing practices. While historically, plants were altered through breeding to change their size or shape, advances in our understanding of plant development and our ability to genetically engineer complex eukaryotes are leading to the direct engineering of plant structure. In this review, I highlight the central role of auxin in plant development and the synthetic biology approaches that could be used to turn auxin-response regulators into powerful tools for modifying plant form. I hypothesize that recoded, gain-of-function auxin response proteins combined with synthetic regulation could be used to override endogenous auxin signaling and control plant structure. I also argue that auxin-response regulators are key to engineering development in nonmodel plants and that single-cell -omics techniques will be essential for characterizing and modifying auxin response in these plants. Collectively, advances in synthetic biology, single-cell -omics, and our understanding of the molecular mechanisms underpinning development have set the stage for a new era in the engineering of plant structure.

Overexpression of cassava RSZ21b enhances drought tolerance in Arabidopsis.

Drought is one of the major environmental constraints affecting crop productivity. Plants have to adjust their developmental and physiological processes to cope with drought. We previously identified 18 cassava serine/arginine-rich (SR) proteins that had a pivotal role in alternative splicing in response to environmental stress. However, functional characterization of SR proteins is rarely explored. Here, we characterized the RSZ subfamily gene MeRSZ21b in cassava. The RSZ21b belongs to the RSZ subfamily, which was widely distributed in major crops and was highly conserved. Quantitative RT-PCR assay showed that the expression of MeRSZ21b was significantly induced by drought. Moreover, overexpression of MeRSZ21b in Arabidopsis was hypersensitive to abscisic acid (ABA) in the phases of seed germination and post-germination seedling growth. Meantime, MeRSZ21b overexpression lines were resistant to sorbitol treatment, and quickly closed the stomata when compared with Col-0 under drought condition. Importantly, overexpression of MeRSZ21b resulted in improved drought tolerance through modulating ABA-dependent signaling. Therefore, our findings refine our knowledge of the SR protein-coding genes and provide novel insights for enhancing plant resistance to environmental stress.

Overexpression of ZmDHN15 Enhances Cold Tolerance in Yeast and Arabidopsis.

Maize (Zea mays L.) originates from the subtropical region and is a warm-loving crop affected by low-temperature stress. Dehydrin (DHN) protein, a member of the Group 2 LEA (late embryogenesis abundant proteins) family, plays an important role in plant abiotic stress. In this study, five maize DHN genes were screened based on the previous transcriptome sequencing data in our laboratory, and we performed sequence analysis and promoter analysis on these five DHN genes. The results showed that the promoter region has many cis-acting elements related to cold stress. The significantly upregulated ZmDHN15 gene has been further screened by expression pattern analysis. The subcellular localization results show that ZmDHN15 fusion protein is localized in the cytoplasm. To verify the role of ZmDHN15 in cold stress, we overexpressed ZmDHN15 in yeast and Arabidopsis. We found that the expression of ZmDHN15 can significantly improve the cold resistance of yeast. Under cold stress, ZmDHN15-overexpressing Arabidopsis showed lower MDA content, lower relative electrolyte leakage, and less ROS (reactive oxygen species) when compared to wild-type plants, as well as higher seed germination rate, seedling survival rate, and chlorophyll content. Furthermore, analysis of the expression patterns of ROS-associated marker genes and cold-response-related genes indicated that ZmDHN15 genes play an important role in the expression of these genes. In conclusion, the overexpression of the ZmDHN15 gene can effectively improve the tolerance to cold stress in yeast and Arabidopsis. This study is important for maize germplasm innovation and the genetic improvement of crops.