Genome-wide analysis of chloride channel-encoding gene family members and identification of CLC genes that respond to Cl

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ORIGINAL ARTICLE

Genome‑wide analysis of chloride channel‑encoding gene family members and identification of CLC genes that respond to ­Cl−/salt stress in upland cotton Xun Liu1 · Boyi Pi1 · Jianwei Pu1 · Cong Cheng1 · Jiajia Fang1 · Bingjun Yu1  Received: 25 August 2020 / Accepted: 19 November 2020 © Springer Nature B.V. 2020

Abstract Chloride channels (CLCs) are kinds of anion transport protein family members that are mainly distributed in cell endomembrane systems of prokaryotic and eukaryotic organisms and mediate anion (­ Cl−, as a representative) transport and homeostasis. Some CLC genes have been reported to be involved in ­Cl−/salt tolerance of plants exposed to NaCl stress. Through BLAST in cotton database, a total of 22 CLCs were identified in genomes A and D in upland cotton (Gossypium hirsutum L.), and except for GhCLC6 and GhCLC17, they formed highly similar homologous genes pairs. According to the prediction in PlantCARE database, many cis-acting elements related to abiotic stress responses, including ABREs, AREs, GT-1s, G-boxes, MYBs, MYCs, etc., were found in the promoters of GhCLCs. qRT-PCR revealed that most GhCLC gene expression was upregulated in the roots and leaves of cotton seedlings under salt stress, and those of homologous GhCLC4/15, GhCLC5/16, and GhCLC7/18 displayed more obvious expression. Furthermore, according to leaf virus-induced gene silencing (VIGS) assay and compared with the salt-stressed GhCLC4/15- and GhCLC7/18-silenced cotton plants, the salt-stressed GhCLC5/16silenced plants displayed relatively better growth with significant increases in both ­Cl− content and ­Cl−/NO3− ratio in the roots and drop of the same parameters in the leaves. These results indicate that homologous GhCLC5/16, with the highest ­NaCl−induced upregulation of expression and the maximum number of MYC cis-acting elements, might be the key members contributing to cotton ­Cl−/salt tolerance by regulating the transport, interaction and homeostasis of ­Cl− and ­NO3−. Keywords  Upland cotton · Chloride channel genes (CLCs) · Gene expression · Cl−/salt tolerance · Virus-induced gene silencing (VIGS) · Cl−/NO3− ratio

Introduction Salinization of irrigation water and soil is one of the major abiotic stress factors that adversely affect plant growth and development, severely reduce crop yield and quality, and increasingly threaten agriculture and food safety worldwide [1–3]. NaCl is the major form of salt stress to crop plants, so ­Na+ and ­Cl− are the main toxic salt ions damaging crop plants subjected to saline environments. ­Na+ toxicity and Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s1103​3-020-06023​-z) contains supplementary material, which is available to authorized users. * Bingjun Yu [email protected] 1



Lab of Plant Stress Biology, College of Life Sciences, Nanjing Agricultural University, Nanjing, China

adaptations in salt-stressed crop plants has been deeply investigated and are widely understood [4, 5]. The roles of ­Cl− in plants mainly includ