Transcriptome analysis reveals differentially expressed ERF transcription factors associated with salt response in cotton

Identification of NHXs in Gossypium species and the positive role of GhNHX1 in salt tolerance

BACKGROUND

Plant Na⁺/H⁺ antiporters (NHXs) are membrane-localized proteins that maintain cellular Na⁺/K⁺ and pH homeostasis. Considerable evidence highlighted the critical roles of NHX family in plant development and salt response; however, NHXs in cotton are rarely studied.

RESULTS

The comprehensive and systematic comparative study of NHXs in three Gossypium species was performed. We identified 12, 12, and 23 putative NHX proteins from G. arboreum, G. raimondii, and G. hirsutum, respectively. Phylogenetic study revealed that repeated polyploidization of Gossypium spp. contributed to the expansion of NHX family. Gene structure analysis showed that cotton NHXs contain many introns, which will lead to alternative splicing and help plants to adapt to high salt concentrations in soil. The expression changes of NHXs indicate the possible differences in the roles of distinct NHXs in salt response. GhNHX1 was proved to be located in the vacuolar system and intensively induced by salt stress in cotton. Silencing of GhNHX1 resulted in enhanced sensitivity of cotton seedlings to high salt concentrations, which suggests that GhNHX1 positively regulates cotton tolerance to salt stress.

CONCLUSION

We characterized the gene structure, phylogenetic relationship, chromosomal location, and expression pattern of NHX genes from G. arboreum, G. raimondii, and G. hirsutum. Our findings indicated that the cotton NHX genes are regulated meticulously and differently at the transcription level with possible alternative splicing. The tolerance of plants to salt stress may rely on the expression level of a particular NHX, rather than the number of NHXs in the genome. This study could provide significant insights into the function of plant NHXs, as well as propose promising candidate genes for breeding salt-resistant cotton cultivars.

ABA signaling is negatively regulated by GbWRKY1 through JAZ1 and ABI1 to affect salt and drought tolerance

GbWRKY1 can function as a negative regulator of ABA signaling via JAZ1 and ABI1, with effects on salt and drought tolerance. WRKY transcription factors play important roles in plant development and stress responses. GbWRKY1 was initially identified as a defense-related gene in cotton and negatively regulates the response to fungal pathogens by activating the expression of JAZ1. Here, we characterized the role of GbWRKY1, an orthologue of the Arabidopsis gene AtWRKY75, in abiotic stress (salt and drought) and established novel connection between JAZ1 and ABA signaling in Arabidopsis. GbWRKY1 is nucleus localized and its expression is significantly induced by treatment with ABA and osmotic stresses NaCl and PEG. Increased levels of expression of GbWRKY1 in transgenic Arabidopsis enhance sensitivity to salt and drought as revealed by seed germination tests and soil stress experiments. Similarly, GbWRKY1 overexpression cotton plants also display increased sensitivity to PEG treatment and drought. Expression analysis shows that the induction of two ABA responsive genes, RAB18 and RD29A by NaCl, mannitol, and ABA treatment is significantly impaired in GbWRKY1 overexpression Arabidopsis lines. GbWRKY1 overexpression Arabidopsis displays a strong ABA-insensitive phenotype at both germination and early stages of seedling development. Further genetic evidence suggested that the ABA-insensitive phenotype of GbWRKY1 overexpression Arabidopsis was dependent on JAZ1, and overexpression of JAZ1 also displayed an ABA-insensitive phenotype. In addition, yeast two hybrid and bimolecular fluorescence complementation assays showed that JAZ1 directly interacts with ABI1, a key negative regulator of ABA signaling. We, therefore, demonstrate that GbWRKY1 acts as a negative regulator of ABA signaling, through an interaction network involving JAZ1 and ABI1, to regulate salt and drought tolerance.

An Overview of Hazardous Impacts of Soil Salinity in Crops, Tolerance Mechanisms, and Amelioration through Selenium Supplementation

Soil salinization is one of the major environmental stressors hampering the growth and yield of crops all over the world. A wide spectrum of physiological and biochemical alterations of plants are induced by salinity, which causes lowered water potential in the soil solution, ionic disequilibrium, specific ion effects, and a higher accumulation of reactive oxygen species (ROS). For many years, numerous investigations have been made into salinity stresses and attempts to minimize the losses of plant productivity, including the effects of phytohormones, osmoprotectants, antioxidants, polyamines, and trace elements. One of the protectants, selenium (Se), has been found to be effective in improving growth and inducing tolerance against excessive soil salinity. However, the in-depth mechanisms of Se-induced salinity tolerance are still unclear. This review refines the knowledge involved in Se-mediated improvements of plant growth when subjected to salinity and suggests future perspectives as well as several research limitations in this field.

Differential Expression of Circular RNAs in Polytocous and Monotocous Uterus during the Reproductive Cycle of Sheep

Simple Summary

The uterus is an important reproductive organ that provides nutrition and place for embryonic development. In this study, we identified circular RNAs by deep sequencing and analyzed their expression in the uteri of polytocous and monotocous sheep (FecB++) during follicular and luteal phases. Gene Ontology (GO) and KEGG enrichment analyses revealed that the source genes of these differential circular RNAs (circRNAs) were mainly enriched in reproductive hormone- and energy metabolism-related pathways. These results provide information on the molecular mechanisms of sheep prolificacy.

Abstract

CircRNA plays important roles in cell proliferation, differentiation, autophagy and apoptosis during development. However, there are few reports on circRNAs related to livestock reproduction. In this study, we identified circRNAs by deep sequencing and analyzed their expression in the uteri of polytocous and monotocous sheep (FecB++) during follicular and luteal phases. There were 147 and 364 circRNAs with differential expression in the follicular and luteal phases, respectively. GO and KEGG enrichment analysis was performed for the host genes of the circRNAs to predict the functions of differentially expressed circRNAs. These source genes were mainly involved in the estrogen signaling pathway, TGFβ signaling pathway, GnRH signaling pathway, oxytocin signaling pathway, pentose phosphate pathway, and starch and sucrose metabolism related to reproduction and energy metabolism. CircRNA expression patterns were validated by RT-qPCR. Our findings provide a solid foundation for the identification and characterization of key important circRNAs involved in reproduction.

Flavonoid accumulation in spontaneous cotton mutant results in red coloration and enhanced disease resistance

Cotton, the leading natural fiber, is cultivated worldwide, but its production is seriously threatened by pathogens. Accordingly, the selection of resistant cultivars has become a key priority of cotton breeding programs. In this study, a spontaneous mutant with red coloration (S156) and a control cultivar (S78) were used as experimental materials for a comparative analysis. Metabolomic analysis revealed the enrichment of flavonoids in S156 leaves compared with S78 leaves, and transcriptomic analysis revealed the upregulated expression of flavonoid biosynthesis genes in S156 leaves relative to S78 leaves. In addition, the red mutant showed a significantly increase in resistance to Verticillium dahliae, a fungal pathogen that poses a major threat to cotton production. The pathogen invasion process was suppressed in the red cotton cultivar. This study reveals the mechanism underlying the red coloration of S156 cotton and indicates the great potential of red cotton in pathogen- and insect-resistant breeding of cotton.