Abstract

To understand the mechanism(s) underlying stress responses and discover new stress-tolerance genes in rice (Oryza sativa L.), expression profiles were obtained for leaf and panicle tissues at seedling, booting and heading stages of indica cultivar Pei’ai 64S plants under cold, drought or heat stresses using the GeneChip Rice Genome Array (Affymetrix) representing 51, 279 transcripts from japonica and indicarice. A large number of genes highly up regulated or down regulated were identified under the stresses. OsXET9 (O. sativa L. xyloglucan endotransglucosylase 9, GenBank accession: NM_001060322) was highly induced in leaf and panicle at all the developmental stages, in response to all stresses, especially in seedling and booting stage under cold stress. Real-time quantitative PCR analysis showed that the result was consensus with GeneChip Rice Genome Array, suggesting that OsXET9 is a multiple stress responsive gene in rice. In order to study its function in stress tolerance, we cloned the cDNA of the gene through amplification by PCR. Sequence analysis showed that the cDNA encodes a protein of 284 amino acid residues with M.W. ≈ 31kD and pI ≈ 5.2. The gene encodes a protein with several conserved domains. Comparison of protein sequences indicates that OsXET9 is closely related to the xyloglucan endotransglycosylase. Analysis of the putative promoter region for candidate cis-regulatory elements using Plant CARE software (http://bioinformatics.psb.ugent.be/webtools/plantcare/html/) identified some cis-elements related to stress responses. Based on these analyses and results obtained, we propose that OsXET9 is a novel candidate gene involved in stress tolerance in rice in addition to the function in metabolism of cell wall.

Keywords: Rice, abiotic stress, microarray, xyloglucan endotransglucosylase.