LbMYB48 positively regulates salt gland development of Limonium bicolor and salt tolerance of plants

Abstract

<i>Limonium bicolor</i> is a dicotyledonous recretohalophyte with several multicellular salt glands on the leaves. The plant can directly secrete excess salt onto the leaf surface through the salt glands to maintain ion homeostasis under salt stress. Therefore, it is of great significance to study the functions of genes related to salt gland development and salt tolerance. In this study, an R1-type MYB transcription factor gene was screened from <i>L. bicolor</i>, named <i>LbMYB48</i>, and its expression was strongly induced by salt stress. Subcellular localization analysis showed that <i>LbMYB48</i> was localized in the nucleus. LbMYB48 protein has transcriptional activation activity shown by transcriptional activation experiments. The density of salt glands in the leaves and the salt secretion capacity of <i>LbMYB48</i>-silenced lines were decremented, as demonstrated by the leaf disc method to detect sodium ion secretion. Furthermore, salt stress index experiments revealed that the ability of <i>LbMYB48</i>-silenced lines to resist salt stress was significantly reduced. <i>LbMYB48</i> regulates salt gland development and salt tolerance in <i>L. bicolor</i> mainly by regulating the expression of epidermal cell development related genes such as <i>LbCPC-like</i> and <i>LbDIS3</i> and salt stress-related genes (<i>LbSOSs</i>, <i>LbRLKs</i>, and <i>LbGSTs</i>) as demonstrated by RNA-seq analysis of LbMYB48-silenced lines. The heterologous over-expression of <i>LbMYB48</i> in <i>Arabidopsis thaliana</i> improves salt tolerance of plants by stabilizing ion and osmotic balance and is likely to be involved in the abscisic acid signaling pathway. Therefore, <i>LbMYB48</i>, a transcriptional activator regulates the salt gland development of <i>L. bicolor</i> and salt tolerance of <i>L. bicolor</i> and <i>A. thaliana.</i>