Functional Analysis Of Arabidopsis HY2 Gene In NaCl Signaling Pathway

In recent years, the world’s agric ultural production and development are affected by the growing problem of soil salinization in the earth. As a major abiotic stress,salt stress affects the growth and development of plants seriously. High salt concentration destroy the balance of ion homeostasis, osmotic balance and causes a variety of secondary stress. Plants have a complex signaling network in response to salt stress, including Ca2+-dependent signaling pathway and Ca2+-independent signaling pathway. At present, the techniques of molecular biology about studying on functions of salt stress- induced genes have become an important method for improving the plant salt-tolerance.In this experiment, we used overexpression of Arabidopsis containing luciferase fluorescent protein for a germination experimental screening under 200 m M Na Cl treatment, and we get a salt-sensitive gene called HY2. The HY2 gene encodes phytochromobilin synthase, which is responsible for the synthesis of phytochrome chromophore in plastid, and involved in the regulation of hypocotyl elongation under R&FR treatment. The N domain of HY2 protain has a stretch of 45 amino acids with features of a chloroplast transit peptide and it locates in the plastid. Then we explore the function of HY2 gene in the Na Cl signal transduction pathway with hy2 mutant at the molecular level. The main results are as follows:(1)The HY2 gene expression in Arabidopsis is not tissue-specific and HY2 gene has a low expression in the root, while it is higher in the flower;(2)The HY2 transcription is salt-induced, and hy2 mutant has a phenotype of salt- unsensive. It indicates that the salt-sensitive HY2 gene may be a negative regu Lator in plant salt stress signal pathways. HY2 protein is not salt- induced;(3)The results of gene expression in response to salt stress show that the HY2 gene responds to salt through an ABA- independent pathway, and hy2 mutant inhibits gene expression of DREB2 A and KIN2 etc under salt tolerance;(4)The salt stress inhibites the elongation of hy2 mutant hypocotyls under red light, and it is more seriously than Col4;(5)The hy2 mutant improves salt tolerance by increasing accumulation of proline and reducing the loss of chlorophyll at a physiological level.