Ectopic Expression of Glycine maxGmNAC109 Enhances Drought Tolerance and ABA Sensitivity in Arabidopsis

RING finger ubiquitin E3 ligase CsCHYR1 targets CsATAF1 for degradation to modulate the drought stress response of cucumber through the ABA-dependent pathway

CsCHYR1 (CHY ZINC-FINGER AND RING PROTEIN1) encodes a RING (Really Interesting New Gene) finger E3 ubiquitin ligase involved in ubiquitin-mediated protein degradation and plays an important role for cucumber to resist drought stress. Here, we obtain one of the candidate proteins CsCHYR1 that probably interacts with CsATAF1 by yeast-two hybrid screening. Subsequently, it is verified that CsCHYR1 interacts with CsATAF1 and has self-ubiquitination activity. When the cysteine residue at 180 in the RING domain of CsCHYR1 is replaced by serine or alanine, ubiquitin could not be transported from E2 to the substrate. CsCHYR1 ubiquitinates CsATAF1 and affects the stability of CsATAF1 when plants are subjected to drought stress. The expression level of CsCHYR1 is increased by 4-fold after ABA treatment at 9 h. The Atchyr1 mutants perform an ABA-hyposensitive phenotype and have a lower survival rate than Col-0 and CsCHYR1 Atchyr1 lines. In addition, CsCHYR1 interacts with CsSnRK2.6. Therefore, our study reveals a CsSnRK2.6-CsCHYR1-CsATAF1 complex to promote the drought stress response by decreasing CsATAF1 protein accumulation and inducing stomatal closure. Those findings provide new ideas for cucumber germplasm innovation from the perspective of biochemistry and molecular biology.

Two trehalase isoforms, produced from a single transcript, regulate drought stress tolerance in Arabidopsis thaliana

Alternative translation initiation of the unique Arabidopsis trehalase gene allows for the production of two isoforms with different subcellular localization, providing enzyme access to both intra- and extra-cellular trehalose. The trehalose-hydrolyzing enzyme trehalase mediates drought stress tolerance in Arabidopsis thaliana by controlling ABA-induced stomatal closure. We now report the existence of two trehalase isoforms, produced from a single transcript by alternative translation initiation. The longer full-length N-glycosylated isoform (AtTRE1L) localizes in the plasma membrane with the catalytic domain in the apoplast. The shorter isoform (AtTRE1S) lacks the transmembrane domain and localizes in the cytoplasm and nucleus. The two isoforms can physically interact and this interaction affects localization of AtTRE1S. Consistent with their role in plant drought stress tolerance, both isoforms are activated by AtCPK10, a stress-induced calcium-dependent guard cell protein kinase. Transgenic plants expressing either isoform indicate that both can mediate ABA-induced stomatal closure in response to drought stress but that the short (cytoplasmic/nuclear) isoform, enriched in those conditions, is significantly more effective.

Ampelopsin Confers Endurance and Rehabilitation Mechanisms in Glycine max cv. Sowonkong under Multiple Abiotic Stresses

The present investigation aims to perceive the effect of exogenous ampelopsin treatment on salinity and heavy metal damaged soybean seedlings (Glycine max L.) in terms of physiochemical and molecular responses. Screening of numerous ampelopsin concentrations (0, 0.1, 1, 5, 10 and 25 μM) on soybean seedling growth indicated that the 1 μM concentration displayed an increase in agronomic traits. The study also determined how ampelopsin application could recover salinity and heavy metal damaged plants. Soybean seedlings were irrigated with water, 1.5% NaCl or 3 mM chosen heavy metals for 12 days. Our results showed that the application of ampelopsin raised survival of the 45-day old salinity and heavy metal stressed soybean plants. The ampelopsin treated plants sustained high chlorophyll, protein, amino acid, fatty acid, salicylic acid, sugar, antioxidant activities and proline contents, and displayed low hydrogen peroxide, lipid metabolism, and abscisic acid contents under unfavorable status. A gene expression survey revealed that ampelopsin application led to the improved expression of GmNAC109, GmFDL19, GmFAD3, GmAPX, GmWRKY12, GmWRKY142, and GmSAP16 genes, and reduced the expression of the GmERF75 gene. This study suggests irrigation with ampelopsin can alleviate plant damage and improve plant yield under stress conditions, especially those including salinity and heavy metals.

Identification and functional characterization of Gh_D01G0514 (GhNAC072) transcription factor in response to drought stress tolerance in cotton

Cotton encounters long-term drought stress problems resulting in major yield losses. Transcription factors (TFs) plays an important role in response to biotic and abiotic stresses. The coexpression patterns of gene networks associated with drought stress tolerance were investigated using transcriptome profiles. Applying a weighted gene coexpression network analysis, we discovered a salmon module with 144 genes strongly linked to drought stress tolerance. Based on coexpression and RT-qPCR analysis GH_D01G0514 was selected as the candidate gene, as it was also identified as a hub gene in both roots and leaves with a consistent expression in response to drought stress in both tissues. For validation of GH_D01G0514, Virus Induced Gene Silencing was performed and VIGS plants showed significantly higher excised leaf water loss and ion leakage, while lower relative water and chlorophyll contents as compared to WT (Wild type) and positive control plants. Furthermore, the WT and positive control seedlings showed higher CAT and SOD activities, and lower activities of hydrogen peroxide and MDA enzymes as compared to the VIGS plants. Gh_D01G0514 (GhNAC072) was localized in the nucleus and cytoplasm. Y2H assay demonstrates that Gh_D01G0514 has a potential of auto activation. It was observed that the Gh_D01G0514 was highly upregulated in both tissues based on RNA Seq and RT-qPCR analysis. Thus, we inferred that, this candidate gene might be responsible for drought stress tolerance in cotton. This finding adds significantly to the existing knowledge of drought stress tolerance in cotton and deep molecular analysis are required to understand the molecular mechanisms underlying drought stress tolerance in cotton.

The Drought-Mediated Soybean GmNAC085 Functions as a Positive Regulator of Plant Response to Salinity

Abiotic stress factors, such as drought and salinity, are known to negatively affect plant growth and development. To cope with these adverse conditions, plants have utilized certain defense mechanisms involved in various aspects, including morphological, biochemical and molecular alterations. Particularly, a great deal of evidence for the biological importance of the plant-specific NAM, ATAF1/2, CUC2 (NAC) transcription factors (TFs) in plant adaptation to abiotic stress conditions has been reported. A previous in planta study conducted by our research group demonstrated that soybean (Glycine max) GmNAC085 mediated drought resistance in transgenic Arabidopsis plants. In this study, further characterization of GmNAC085 function in association with salt stress was performed. The findings revealed that under this condition, transgenic soybean plants overexpressing GmNAC085 displayed better germination rates than wild-type plants. In addition, biochemical and transcriptional analyses showed that the transgenic plants acquired a better defense system against salinity-induced oxidative stress, with higher activities of antioxidant enzymes responsible for scavenging hydrogen peroxide or superoxide radicals. Higher transcript levels of several key stress-responsive genes involved in the proline biosynthetic pathway, sodium ion transporter and accumulation of dehydrins were also observed, indicating better osmoprotection and more efficient ion regulation capacity in the transgenic lines. Taken together, these findings and our previous report indicate that GmNAC085 may play a role as a positive regulator in plant adaptation to drought and salinity conditions.

The NAC-type transcription factor GmNAC20 improves cold, salinity tolerance, and lateral root formation in transgenic rice plants

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 T3 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, T3 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.

Ectopic expression of GmHP08 enhances resistance of transgenic Arabidopsis toward drought stress

Ectopic expression of Glycine max two-component system member GmHP08 in Arabidopsis enhanced drought tolerance of transgenic plants, possibly via ABA-dependent pathways. Phosphorelay by two-component system (TCS) is a signal transduction mechanism which has been evolutionarily conserved in both prokaryotic and eukaryotic organisms. Previous studies have provided lines of evidence on the involvement of TCS genes in plant perception and responses to environmental stimuli. In this research, drought-associated functions of GmHP08, a TCS member from soybean (Glycine max L.), were investigated via its ectopic expression in Arabidopsis system. Results from the drought survival assay showed that GmHP08-transgenic plants exhibited higher survival rates compared with their wild-type (WT) counterparts, indicating better drought resistance of the former group. Analyses revealed that the transgenic plants outperformed the WT in various regards, i.e. capability of water retention, prevention of hydrogen peroxide accumulation and enhancement of antioxidant enzymatic activities under water-deficit conditions. Additionally, the expression of stress-marker genes, especially antioxidant enzyme-encoding genes, in the transgenic plants were found greater than that of the WT plants. In contrary, the expression of SAG13 gene, one of the senescence-associated genes, and of several abscisic acid (ABA)-related genes was repressed. Data from this study also revealed that the ectopic expression lines at germination and early seedling development stages were hypersensitive to exogenous ABA treatment. Taken together, our results demonstrated that GmHP08 could play an important role in mediating plant response to drought, possibly via an ABA-dependent manner.

The BTB-TAZ protein MdBT2 negatively regulates the drought stress response by interacting with the transcription factor MdNAC143 in apple

Drought stress is a severe source of abiotic stress that can affect apple yield and quality, yet the underlying molecular mechanism of the drought stress response and the role of MdBT2 in the process remain unclear. Here, we find that MdBT2 negatively regulates the drought stress response. Both in vivo and in vitro assays indicated that MdBT2 interacted physically with and ubiquitinated MdNAC143, a member of the NAC TF family that is a positive regulator under drought stress. In addition, MdBT2 promotes the degradation of MdNAC143 via the 26S proteasome system. A series of transgenic assays in apple calli and Arabidopsis verify that MdBT2 confers susceptibility to drought stress at least in part by the regulation of MdNAC143. Overall, our findings provide new insight into the mechanism of MdBT2, which functions antagonistically to MdNAC143 in regulating drought stress by regulating the potential downstream target protein MdNAC143 for proteasomal degradation in apple.

Heterologous Expression of a Soybean Gene RR34 Conferred Improved Drought Resistance of Transgenic Arabidopsis

Two-component systems (TCSs) have been identified as participants in mediating plant response to water deficit. Nevertheless, insights of their contribution to plant drought responses and associated regulatory mechanisms remain limited. Herein, a soybean response regulator (RR) gene RR34, which is the potential drought-responsive downstream member of a TCS, was ectopically expressed in the model plant Arabidopsis for the analysis of its biological roles in drought stress response. Results from the survival test revealed outstanding recovery ratios of 52%-53% in the examined transgenic lines compared with 28% of the wild-type plants. Additionally, remarkedly lower water loss rates in detached leaves as well as enhanced antioxidant enzyme activities of catalase and superoxide dismutase were observed in the transgenic group. Further transcriptional analysis of a subset of drought-responsive genes demonstrated higher expression in GmRR34-transgenic plants upon exposure to drought, including abscisic acid (ABA)-related genes NCED3, OST1, ABI5, and RAB18. These ectopic expression lines also displayed hypersensitivity to ABA treatment at germination and post-germination stages. Collectively, these findings indicated the ABA-associated mode of action of GmRR34 in conferring better plant performance under the adverse drought conditions.

The Soybean GmNAC019 Transcription Factor Mediates Drought Tolerance in Arabidopsis in an Abscisic Acid-Dependent Manner

Being master regulators of gene expression, transcription factors (TFs) play important roles in determining plant growth, development and reproduction. To date, many TFs have been shown to positively mediate plant responses to environmental stresses. In the current study, the biological functions of a stress-responsive NAC [NAM (No Apical Meristem), ATAF1/2 (Arabidopsis Transcription Activation Factor1/2), CUC2 (Cup-shaped Cotyledon2)]-TF encoding gene isolated from soybean (GmNAC019) in relation to plant drought tolerance and abscisic acid (ABA) responses were investigated. By using a heterologous transgenic system, we revealed that transgenic Arabidopsis plants constitutively expressing the GmNAC019 gene exhibited higher survival rates in a soil-drying assay, which was associated with lower water loss rate in detached leaves, lower cellular hydrogen peroxide content and stronger antioxidant defense under water-stressed conditions. Additionally, the exogenous treatment of transgenic plants with ABA showed their hypersensitivity to this phytohormone, exhibiting lower rates of seed germination and green cotyledons. Taken together, these findings demonstrated that GmNAC019 functions as a positive regulator of ABA-mediated plant response to drought, and thus, it has potential utility for improving plant tolerance through molecular biotechnology.