Characterization of Glossy1-Homologous Genes of Rice Involved in Leaf Wax Accumulation and Drought Resistance

摘要

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 11homologous genes of GL1 in rice, designated OsGL1l-1～OsGL1-11. OsGL1-1,-2 and -3 are closely related to GL1. OsGL1-4,-5,-6, and-7 are closely related to ArabidopsisCER1 that is involved in cuticular wax biosynthesis. OsGL1-8,-9,-10 and -11 are closely related to SUR2 encoding a putative sterol denaturize also involved in epicuticular wax biosynthesis. Genes showed variable expression levels in different tissues and organs of rice, and most of them were induced by a biotic stresses. to the wild type, the OsGL1-2-over-expression rice exhibited more wax crystallization and a thick erepicuticular 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 cubicula 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 cubicula wax in the and increase of total cuticular wax in the over-expression plants. Compared to the over-expression and wild type plants, the osgl2 -2 mutants was more sensitive to drought stress at reproductive stage, suggesting an important role of this gene in drought resistance.

目录

英文文摘

Abbreviations

1 Review of literature

1.1 Overview

1.2 What is cuticle and cuticular wax

1.3 Cuticular wax biosynthesis

1.4 Multiple elongation system

1.5 Synthesis of very long chain fatty acid wax precursors

1.6 Regulation of wax biosynthesis

1.7 Glossy mutant (gl) defective or altered in wax production

1.8 Agrobacterium-mediated transformation

1.9 Selectable and reporter marker genes

1.10 T-DNA intertional mutagenesis

2 Aim and significance

3 Materials and methods

3.1 Identification and sequence analysis of GL1-homologous genes in rice

3.2 Plant growth and treatments

3.3 Transcript level analysis of GL1-like gene family in rice

3.4 Over-expression of homologous genes

3.5 Genotypic screening of mutant osgll-2 plants

3.6 Phenotyping and measurements oftransgenie and mutant plants

3.6.1 Stress in field condition

3.6.2 Measurement of plant height, tiller number and observation of plants development

3.6.3 Chlorophyll leaching and water loss measurement

3.7 Scanning electronic microscopy (SEM) and transmission electron microscopy (TEM) observations

3.8 Wax extraction and quantification

4 Results

4.1 Identification of GL1 homologous genes in rice

4.2 Phylogenetic analysis of GL1-like gene family

4.3 Expression profile of OsGL1-like gene family in tissues and organs

4.4 Responsiveness of OsGL1 genes to abiotic stresses

4.5 Over-expression of the homologous genes

4.6 Reduced growth, altered drought resistance and cuticular permeability in OsGL1-2 over-expression and mutant rice plants

4.7 Altered wax accumulation in the OsGL1-2 over-expression and mutant rice plants

5 Discussions

5.1 OsGL1 homologs, WAX2, and CERlare from same ancestor

5.2 Expressions of the OsGLl-like genes are tissue-or organ specific and osgl1-2 mutant is sensitive to drought

5.3 The osgl1-2 mutant affects cuticular wax accumulation and biosynthesis

5.4 Future prospectus

References

Protocols

Resume

Acknowledgement