Sea-island cotton (Gossypium barbadense L.) GbTCP5 improves plant adaptation to drought and salt stress by directly activating GbERD7, GbUBC19, and GbGOLS2 expression

Cotton is one of the most important cash crops in the world. Most of its production areas are in arid or semiarid regions, and drought and salinity seriously affect cotton production. Plant teosinte branched1/cycloidea/ proliferating cell factor 1 (TCP) transcription factors play a pivotal role in abiotic stress responses. However, the role of TCPs in the abiotic stress response in cotton has not been fully elucidated. Here, the function of the GbTCP5 transcription factor in the responses to drought and salt stresses was identified. The expression of GbTCP5 was induced by drought, salt, and abscisic acid (ABA) treatments. The exposure of 35S:GbTCP5 transgenic Arabidopsis to drought stress increased its survival rate and ABA content and decreased its leaf water loss rate and malondialdehyde (MDA) content compared with those of the wild type (WT). In addition, the expression levels of the stress response genes AtCOR15, AtCOR414, AtRD29A, AtLTP4, and AtPUB22 and the ABA biosynthesis-related gene AtNCED3 were significantly higher in 35S:GbTCP5 transgenic lines than in the WT. The exposure of 35S:GbTCP5 transgenic Arabidopsis to salt stress accelerated its germination rate, increased its root length, survival rate and chlorophyll content, and decreased the MDA content compared with those of the WT. Under drought or salt stress, cotton with virus-induced gene silencing of GbTCP5 showed a decreased survival rate, a shorter root length, a smaller root area, a reduced root volume and a higher MDA content compared with pTRV2 cotton. Transcriptome sequencing results confirmed that GbTCP5 was involved in several abiotic stressrelated metabolic pathways. The results confirmed that GbTCP5 protein activated the expression of GbGLOS2, GbUBC19, and GbERD7 and then participated in the drought and salt tolerance of cotton by binding to the TCP cis-acting element in the promoter regions of these genes. All the above results prove that GbTCP5 plays a positive role in plant responses to drought and salt stress.