Poster: Late and Moved Abstracts

Abs # 1416: Submergence-induced leaf elongation is suppressed in transgenic rice by the Ras-GTP signalling from the submergence tolerance strain

Presenter:	Vanavichit, Apichart , apichart@dna.kps.ku.ac.th
Authors	Vanavichit, Apichart  (B) (A)  Ruangjaichol, Vinitcharn  (A)   Nimlek, Aekapop  (A)   Sangsraku, Duangjai  (A)   Siangliw, Meechi  (A)   Toojinda, Theerayut  (A)   Tragoonrung, Somvong  (C) (A)
Affiliations:	(A): Rice Gene Discovery, National Center for Genetic Engineering and Biotecnology (B): Kasetsart University (C): DNA Technology Laboratory

Flash flooding is a common natural disaster in monsoon rice production. In susceptible rice strains, rapid leaf elongation can be observed two days after complete flooding and the whole canopy senesce if their leaves fail to reach the water surface. In submergence tolerance strains, leaf elongation is normally slow, their canopy stay green and rapid recovery after desubmergence. The major QTL for submergence tolerance (Sub) was mapped on 6 cM of the chromosome 9 where extensive fine-scale mapping and high-throughput sequencing were accomplished. Three candidate genes identified within this region were Ras-related GTP binding protein (Ras), Ethylene responsive element binding protein (EREBP) and hypothetical protein. The genomic fragment including the coding sequence and its promotor of Ras from FR13A, the submergence tolerance strain, was transformed into a susceptible rice strain using a particle gun bombardment. In order to compare the expression of the two alleles during submerging conditions, TaqMan PCR probes were designed to specifically detect a single nuleotide polymorphism (SNP) identified in the exon 1. This SNP was the substitution of G in the susceptible strain for T in the tolerance strain. The expression of the tolerance allele driven by its native promotor in the transgenic plant was maximized at 2 days while the expression of the susceptible allele was increased slowly to the peak in 6 days. The transgenic rice had slow leaf elongation just like the tolerance rice while the control plant elongate rapidly under flooding conditions. This transgenic Ras behave similar to the isogenic lines developed for Ras by backcrossing. The molecular models discussing how Ras plays roles in regulating the leaf elongation induced by submergence.