Cotton is a globally important cash crop. Verticillium wilt (VW) is commonly known as “cancer” of cotton and causes serious loss of yield and fiber quality in cotton production around the world. Here, we performed a BSA-seq analysis using an F_2:3 segregation population to identify the candidate loci involved in VW resistance. Two QTLs (qvw-D05-1 and qvw-D05-2) related to VW resistance in cotton were identified using two resistant/susceptible bulks from the F₂ segregation population constructed by crossing the resistant cultivar ZZM2 with the susceptible cultivar J11. A total of 30stop-lost SNPs and 42 stop-gained SNPs, which included 17 genes, were screened in the qvw-D05-2 region by SnpEff analysis. Further analysis of the transcriptome data and qRT-PCR revealed that the expression level of Ghir_D05G037630 (designated as GhDRP) varied significantly at certain time points after infection with V. dahliae. The virus-induced gene silencing of GhDRP resulted in higher susceptibility of the plants to V. dahliae than the control, suggesting that GhDRP is involved in the resistance to V. dahlia infection. This study provides a method for rapid mining of quantitative trait loci and screening of candidate genes, as well as enriches the genomic information and gene resources for the molecular breeding of disease resistance in cotton.

Verticillium wilt is one of the most destructive diseases affecting global cotton production. The most effective way to control wilt disease has been the development of new cotton varieties that are resistant to VW. VW-resistant Upland cotton cultivars have been created in both the USA and China by Gossypium barbadense introgression. More than 100 VW resistance quantitative trait loci have been detected. Three clustered VW resistance-related QTL were detected in a 120-line association population and assigned to a genome region of 14,653,469–55,190,112 bp in Dt_chr9. A regional association analysis-based fine-mapping strategy was developed to narrow down the confidence intervals of the above QTL. The estimated LD decay of the genome region of interest was much faster than those of the Dt_chr9 chromosome and the whole genome, suggesting the existence of a recombination hotspot. Thirty-seven haplotype blocks were detected. The confidence intervals of the three clustered QTL were narrowed down to a region of 937,906 bp involving QTL-i23734Gh and a region of 1,389,417 bp involving QTL- i10740Gh, respectively. Each region contained the strongest association signal. Comparative analysis redefined the confidence intervals of the other three QTLs, qDL52T2-c19, QTL-BNL4069, and QTL-JESPR0001. The broad-spectrum VW resistance QTL qVW-D9–1 was demonstrated to be closely linked with the three redefined QTL, QTL-i23734Gh, QTL- i10740Gh and QTL-JESPR0001. Twelve functional genes were detected to be located within the redefined confidence intervals of VW resistance QTL. The mRNA CotAD_60243, encoding E3 ubiquitin-protein ligase UPL2-like, responsible for plant innate immunity and broad-spectrum disease resistance, was found to be overlapped with the strongest association signal i10740Gh. Six mRNAs encoding putative disease-resistance proteins were within the redefined confidence interval of QTL-JESPR0001, suggesting a tandem arrangement of R genes. Our results proved that the VW resistance effect related to three clustered VW resistance-related QTL was actually controled by two redefined major QTL and severlal minor loci. The broad-spectrum VW resistance QTL qVW-D9–1 may be closely linked with the two redefined major QTLs. The tandem arrangement of R genes were detected in the redefined confidence interval of QTL-JESPR0001. The candidate genes obtained should be helpful in identifying and characterizing defense genes related to VW resistance QTL.

Climate deterioration, water shortages, and abiotic stress are the main threats worldwide that seriously affect cotton growth, yield, and fiber quality. Therefore, research on improving cotton yield and tolerance to biotic and abiotic stresses is of great importance. The NAC proteins are crucial and plant-specific transcription factors (TFs) that are involved in cotton growth, development, and stress responses. The comprehensive utilization of cotton NAC TFs in the improvement of cotton varieties through novel biotechnological methods is feasible. Based on cotton genomic data, genome-wide identification and analyses have revealed potential functions of cotton NAC genes. Here, we comprehensively summarize the recent progress in understanding cotton NAC TFs roles in regulating responses to drought, salt, and Verticillium wilt-related stresses, as well as leaf senescence and the development of fibers, xylem, and glands. The detailed regulatory network of NAC proteins in cotton is also elucidated. Cotton NAC TFs directly bind to the promoters of genes associated with ABA biosynthesis and secondary cell-wall formation, participate in several biological processes by interacting with related proteins, and regulate the expression of downstream genes. Studies have shown that the overexpression of NAC TF genes in cotton and other model plants improve their drought or salt tolerance. This review elucidates the latest findings on the functions and regulation of cotton NAC proteins, broadens our understanding of cotton NAC TFs, and lays a fundamental foundation for further molecular breeding research in cotton.

Background: Cotton is extremely affected by severe natural stresses. Drought is one of the most serious abiotic stress that adversely influences cotton growth, productivity, and fiber quality. Previous studies indicate that basic leucine-zipper (bZIP) transcription factors are involved in the response of plants to various stresses. However, the molecular function and regulatory mechanism of GhVIP1 in response to drought stress are still unknown. Results: In this research, GhVIP1 was cloned from a drought-tolerant variety. Expression of GhVIP1 was up-regulated in response to multiple abiotic stresses, especially under drought stress. And GhVIP1 was highly expressed in the root, stem, and 10 days post-anthesis ovule. Inhibiting the expression of GhVIP1 in cotton using the virus-induced gene silencing method resulted in higher electrical conductivity in leaves, but lower water content under drought stress compared with the WT plant. Overexpression of GhVIP1 in Arabidopsis enhanced plant drought tolerance through increasing the seed germination rate and improving the development of root. The exogenous expression of GhVIP1 up-regulated the transcription of genes associated with drought response and proline biosynthesis during drought stress in Arabidopsis. Conclusion: In summary, these results indicated that GhVIP1 played a positive role in plants' response to drought stress. The use of GhVIP1 via modern biotechnology might facilitate the improvement of drought tolerance in cotton cultivars.

Verticillium wilt is a serious soil-borne vascular disease that causes major losses to upland cotton (Gossypium hirutum L.) worldwidely every year. The protein VIP1 (VirE2 interaction protein 1), a bZIP transcription factor, is involved in plant response to many stress conditions, especially pathogenic bacteria. However, its roles in cotton response to Verticillium wilt are poorly understood. The GbVIP1 gene was cloned from resistant sea-island cotton (G. barbadense) cv. Hai 7124. Expression of GbVIP1 was up-regulated by inoculation with Verticillium dahliae and exogenous treatment with ethylene. Results of virus-induced gene silencing suggested that silencing of GbVIP1 weakened cotton resistance to Verticillium wilt. The heterologous expression of GbVIP1 in tobacco showed enhanced resistance to Verticillium wilt. The PR1, PR1-like and HSP70 genes were up-regulated in GbVIP1 transgenic tobacco after Verticillium wilt infection. Our results suggested that GbVIP1 increased plant resistance to Verticillium wilt through up-regulating expressions of PR1, PR1-like, and HSP70. These results provide new approaches to improving resistance to Verticillium wilt in upland cotton and also have great potential for disease-resistance breeding of cotton.