Characterization of Glossy1-Homologous Genes of Rice Involved in Leaf Wax Accumulation and Drought Resistance
The vital importance of plant surface wax in protecting tissue from environmental stresses is reflected in the huge commitment of epidermal cells to cuticle formation. Glossy 1 (GL1) is one of the reported genes controlling wax synthesis. This study aimed to identify GL1-homologous genes in Oryza sativa and characterize the key members of this family involved in wax synthesis and stress resistance. Sequence analysis revealed 11 homologous genes of GL1 in rice, designated OsGL1-1-OsGL1-11. OsGL1-1,-2 and-3 are closely related to GL1. OsGL1-4,-5,-6, and -7 are closely related to Arabidopsis CER1 that is involved in cuticular wax biosynthesis. OsGL1-8,-9,-10 and -11 are closely related to SUR2 encoding a putative sterol desaturase also involved in epicuticular wax biosynthesis. These genes showed variable expression levels in different tissues and organs of rice, and most of them were induced by abiotic stresses. Compared to the wild type, the OsGL1-2-over-expression rice exhibited more wax crystallization and a thicker epicuticular layer; while the mutant of this gene showed less wax crystallization and a thinner cuticular layer. Chlorophyll leaching and water loss experiment suggested that the cuticular permeability was decreased and increased in the over-expression lines and the mutant, respectively. To identify additional components involved in cuticular wax production, the role of the OsGL1-2 gene, defective in the osgl1-2 mutant were investigated. Quantification analysis of wax composition by GC-MS revealed a significant reduction of total cuticular wax in the mutant and increase of total cuticular wax in the over-expression plants. Compared to the over-expression and wild type plants, the osgl1-2 mutant was more sensitive to drought stress at reproductive stage, suggesting an important role of this gene in drought resistance.