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• The cotton cytoplasmic subgroup gene GhHSP70-26 is transcribed in response to polyethylene glycol and abscisic acid treatment and salt, cold, and heat stress. • Overexpression of the GhHSP70-26 gene in tobacco and silencing of the GhHSP70-26 gene in cotton showed that the GhHSP70-26 gene can improve plant tolerance to drought stress. • GhbZIP43 and GhHSF8 bind to cis -acting ABREs and HSEs, respectively, to regulate the transcription of GhHSP70-26 , and the GhHSP70-26 protein interacts with the GhAPX2 protein. The 70-kDa heat shock protein (HSP70) is a molecular chaperone that plays an important role in the response of plants to abiotic stress, but the function and molecular mechanism of HSP70 in the cotton drought stress response are unclear. In this study, the HSP70-encoding gene GhHSP70-26 , which belongs to the cytoplasmic HSP70 subgroup, was cloned from upland cotton (Gossypium hirsutum L.). The transcript level of GhHSP70-26 in cotton leaves was higher than that in cotton stems and roots. GhHSP70-26 was found to respond at the transcriptional level to polyethylene glycol (PEG) and abscisic acid (ABA) treatment and to cold, salt, and heat stress, and its transcript level was positively correlated with the drought resistance of different cotton varieties. Heterologous overexpression of the GhHSP70-26 gene improved the drought resistance of transgenic tobacco compared with that of wild-type (WT) tobacco, and the transgenic tobacco plants were characterized by low leaf wilting, high survival, low leaf water loss, increased root length and high chlorophyll content. Moreover, the transgenic tobacco plants overexpressing GhHSP70-26 had higher proline contents, higher superoxide dismutase (SOD) and peroxidase (POD) enzyme activities, and lower malondialdehyde (MDA) and reactive oxygen species (ROS) contents than the WT tobacco plants. The transcript levels of the stress response-related genes NtLEA , NtERD10D , NtPOD , NtSOD , and NtNCED3-1 in transgenic tobacco overexpressing GhHSP70-26 were significantly higher than those in WT tobacco. In contrast, under drought stress, unlike the results obtained with the pTRV2 empty vector (EV)-transformed and WT cotton plants, the use of virus-induced gene silencing (VIGS) technology to silence the GhHSP70-26 gene in cotton resulted in plants with severely wilted leaves, an increased water loss rate, a higher MDA content, and higher relative electrical conductivity (REC). Furthermore, yeast one-hybrid assays showed that GhbZIP43 and GhHSF8 bind to ABA-responsive elements (ABREs) and heat shock elements (HSEs) in the GhHSP70-26 promoter, respectively. Moreover, yeast two-hybrid, bimolecular fluorescence complementation and luciferase complementation assays showed that the GhHSP70-26 protein interacts with the ascorbate peroxidase (APX) GhAPX2 protein. These results indicate that by reducing the degrees of cell membrane damage and cellular damage caused by ROS stress, the GhHSP70-26 protein plays a positive role in the response of plants to drought stress. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) have important functions in the plant salt stress response. However, the functions of nonconserved miRNAs in soybean salt stress adaptation remain unclear. In this study, the soybean nonconserved miRNA gma-miR4359b and its target mRNA F-box gene GmFBX193 were functionally identified in response to salt stress. gma-miR4359b responded to salt stress in soybean hairy roots, stems, and leaves. Under salt stress, the root length ratio, root surface area ratio, root volume ratio, root tip number, survival rate, chlorophyll content, soluble sugar content, proline content, superoxide dismutase activity, and peroxidase enzyme activity of soybean hairy roots overexpressing gma-miR4359b (MIR4359b) were increased compared to those of the K599 (control) soybean hairy roots, while the relative electrolyte leakage and malondialdehyde content of the MIR4359b soybean hairy roots decreased. In contrast, soybean hairy roots in which target mimicry (MIM4359b) and short tandem target mimic (STTM4359b) inhibited gma-miR4359b exhibited a salt-sensitive phenotype. The transcription level of GmFBX193 was decreased in MIR4359b soybean hairy roots, while the transcription level of GmFBX193 was increased in MIM4359b and STTM4359b soybean hairy roots. GmFBX193 responded to salt stress in soybean roots, and GmFBX193 was identified as a nuclear-localized protein. Under salt stress, soybean hairy roots overexpressing GmFBX193 had a similar phenotype to MIM4359b and STTM4359b soybean hairy roots. Compared with K599 (control) soybean hairy roots, MIR4359b soybean hairy roots had 172 differentially expressed genes (DEGs), and MIM4359b soybean hairy roots had 2129 DEGs. Some known stress-related transcription factors were included among the DEGs. Taken together, these results suggest that gma-miR4359b plays a positive role in the soybean salt stress response by negatively regulating GmFBX193. • The nonconserved soybean miRNA gma-miR4359b and its target mRNA F-box gene GmFBX193 responded to salt stress. gma-miR4359b positively regulates the soybean response to salt stress by targeting GmFBX193. • gma-miR4359b is a positive regulator of salt tolerance in soybean. • GmFBX193 negatively regulates soybean tolerance to salt stress. • Transcriptome sequencing showed that gma-miR4359b could affect the transcription levels of some transcription factors related to the salt stress response. [ABSTRACT FROM AUTHOR]

• The GmNF-YA10 gene encodes an NF-YA transcription factor located in the nucleus that responds to PEG and ABA treatment at the transcription level. • Overexpression of the GmNF-YA10 gene increases the drought resistance of transgenic Arabidopsis by accumulating osmotic substances, slowing membrane lipid peroxidation, enhancing photosynthesis, regulating ABA-mediated stomatal closure, reducing the leaf water loss rate, and affecting the transcript levels of stress-related genes. • GmNF-YA10 gene participates in Arabidopsis response to drought stress through two pathways, ABA-dependent and ABA-independent. Nuclear factor (NF)-Y is composed of three subunits, NF-YA, NF-YB and NF-YC, and plays important roles in the regulation of plant abiotic stress response gene expression. However, the function of individual soybean NF-YA proteins in response to drought stress is unclear. In this study, the soybean NF-YA subunit gene GmNF-YA10 was cloned, and its function in response to drought stress was identified. GmNF-YA10 is broadly expressed in soybean tissues and is specifically located in the nucleus. In soybean roots, the transcription level of the GmNF-YA10 gene was induced by polyethylene glycol (PEG)-simulated drought stress and abscisic acid (ABA) treatment. Under mannitol stress, the germination rate of transgenic Arabidopsis overexpressing GmNF-YA10 was higher than that of wild-type (WT) Arabidopsis. After drought stress, the survival rate, relative water content, ABA content, proline content and chlorophyll content of transgenic Arabidopsis overexpressing GmNF-YA10 were higher than those of WT Arabidopsis while the rate of water loss and the contents of malondialdehyde and sucrose were lower than those of WT Arabidopsis , indicating that transgenic Arabidopsis overexpressing GmNF-YA10 has better drought resistance than WT Arabidopsis. Under the ABA treatment, the root length of transgenic Arabidopsis overexpressing GmNF-YA10 was shorter than that of WT Arabidopsis and the degree of stomatal closure was greater than that of WT Arabidopsis , indicating that transgenic Arabidopsis overexpressing GmNF-YA10 was more sensitive to ABA at the post-germination stage. Transcriptome sequencing and real-time quantitative PCR analysis showed that GmNF-YA10 affected the expression of both ABA-dependent and ABA-independent signalling pathway genes. These results indicate that GmNF-YA10 significantly improves the drought resistance of transgenic Arabidopsis through ABA-dependent and ABA-independent signal transduction pathways. [ABSTRACT FROM AUTHOR]

• GmFBX176 encodes a nuclear-localized F-box protein that responds to PEG treatment, ABA treatment, and salt stress at the transcriptional level. • Stress tolerance analysis of heterologous GmFBX176-overexpressing Arabidopsis revealed that GmFBX176 is a negative regulatory protein that improves tolerance to drought and salt stress. • GmFBX176-overexpressing Arabidopsis displayed reduced sensitivity to ABA. • Constitutive heterologous overexpression of the GmFBX176 gene affects stress-related physiological indicators and the transcript levels of stress response genes in transgenic Arabidopsis. As key components of the E3 ubiquitin ligase in the Skp1/Cullin or CDC53/F-box (SCF) complex, F-box proteins are involved in plant abiotic stress responses. However, the functions of F-box proteins in soybean in response to abiotic stress remain unclear. In this study, the soybean F-box protein-encoding gene GmFBX176 was cloned and functionally analyzed. GmFBX176 localized to the nucleus, was widely expressed in tissues (with the highest level in the roots), and responded to polyethylene glycol (PEG) treatment, abscisic acid (ABA) treatment, and salt stress at the transcriptional level. GmFBX176 -overexpressing Arabidopsis had lower survival rates; faster water loss rates; lower proline, sucrose and chlorophyll contents; greater malondialdehyde (MDA) contents; greater relative electrical conductivity (REC); and greater drought stress sensitivity than did wild-type (WT) Arabidopsis. Moreover, GmFBX176 -overexpressing Arabidopsis had lower survival rates, lower chlorophyll content, lower superoxide dismutase (SOD) activity, greater sensitivity to salt stress, longer roots, greater stomatal opening rates, and lower sensitivity to ABA than did WT Arabidopsis. Transcriptome sequencing and quantitative real-time PCR (qPCR) analyses revealed that GmFBX176 affects the transcript levels of stress response genes. These results indicate that GmFBX176 regulates ABA-mediated responses to drought and salt stress. [ABSTRACT FROM AUTHOR]