Identification and Functional Analysis of Differentially Expressed Genes in Plant Response to Abiotic Stresses

Heat shock transcription factor (HSF) is an important TF that performs a dominant role in plant growth, development, and stress response network. In this study, we identified a total of 30 HSF members from poplar, which are unevenly distributed on 17 chromosomes. The poplar HSF family can be divided into three subfamilies, and the members of the same subfamily share relatively conserved domains and motifs. HSF family members are acidic and hydrophilic proteins that are located in the nucleus and mainly carry out gene expansion through segmental replication. In addition, they have rich collinearity across plant species. Based on RNA-Seq analysis, we explored the expression pattern of PtHSFs under salt stress. Subsequently, we cloned the significantly upregulated PtHSF21 gene and transformed it into Populus simonii × P. nigra. Under salt stress, the transgenic poplar overexpressing PtHSF21 had a better growth state and higher reactive oxygen scavenging ability. A yeast one-hybrid experiment indicated PtHSF21 could improve salt tolerance by specifically binding to the anti-stress cis-acting element HSE. This study comprehensively profiled the fundamental information of poplar HSF family members and their responses to salt stress and specifically verified the biological function of PtHSF21, which provides clues for understanding the molecular mechanism of poplar HSF members in response to salt stress.

Cotton (Gossypium hirsutum L.) is the world’s most economically valuable textile crop. However, cotton plants are often subjected to numerous abiotic stresses that can dramatically limit yield. Trihelix transcription factors (TTFs) play important roles in abiotic stress responses in many plant species, and efforts to better understand their roles in cotton abiotic stress responses are ongoing. In this study, a member of the cotton TTF family (GhGT23) was functionally characterized. This protein contains a SANT domain and is a member of the SIP subfamily of TTF proteins. GhGT23 was significantly (p < 0.05) and highly expressed in cotton fiber compared to relatively low expression in other tissues. A significant (p < 0.05) increase in GhGT23 expression occurred in cotton seedlings within 12 hours of drought, salt, and ABA exposure. The GhGT23 protein localized in the nucleus but exhibited no signs of transactivation activity. GhGT23 overexpression in Arabidopsis conferred enhanced drought and salt stress tolerance. The expression of stress-related genes was higher in transgenic Arabidopsis expressing GhGT23 than in wild-type plants subjected to salt stress. The results of electrophoretic mobility shift assay revealed that GhGT23 could bind to the GT cis-elements GT-1Box (Box II), GT2-Box, GT3-Box, GT-3a (Site1-type), GT-3b, and Box as well as the MYB cis-elements MBS1 and MRE4. Our results demonstrate that GhGT23 positively regulates salt and drought stress responses, possibly by enhancing the expression of stress-related genes.

Membrane transporters encoded by NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER (NPF) genes, which play crucial roles in plant growth, development and resistance to various stresses, are involved in the transport of nitrate (NO₃^-) and peptides. In several plant species, NPF genes are involved in the resistance to abiotic stresses; however, whether the whole NPF gene family in cotton contributes to this resistance has not been systematically investigated. Here, 201 genes encoding NPF proteins with a peptide transporter (PTR) domain were confirmed in three different Gossypium species, namely, Gossypium hirsutum, Gossypium arboreum and Gossypium raimondii. The NPF proteins in these three Gossypium species and Arabidopsis thaliana were classified into three different subfamilies via phylogenetic analysis. Among the genes that encode these proteins, most GhNPF genes in the same subfamily contained similar gene structures and conserved domains. Predictions of the promoters of these genes revealed that the cis-acting elements included phytohormone- and light-responsive elements, indicating that some of these genes might be expressed in response to abiotic stress. Furthermore, 52 common potential candidate genes in 98 GhNPFs were predicted to exhibit specific spatiotemporal expression patterns in different tissues based on two RNA sequencing (RNA-seq) datasets. Finally, the gene expression profiles of abiotic stress indicated that 31 GhNPF genes were upregulated in at least one treatment period. Under abiotic stress for 12 and 24 h, the expression of GhNPF8 was upregulated upon cold treatment but downregulated with heat treatment, salt treatment and drought treatment. Furthermore, the expression of genes GhNPF8, GhNPF54 and GhNPF43 peaked at 6 h after heat and salt treatment. These results indicated that these genes exhibit underlying characteristics related to responses to abiotic stress. The verification of NPFs and analysis of their expression profiles in different tissues and in response to different abiotic stresses of cotton provide a basis for further studying the relationship between abiotic stress resistance and nitrogen (N) transport in cotton, as well as identifying candidate genes to facilitate their functional identification.