Transcriptomic analysis of four soybean genotypes in response to water stress

E.M. PARDO, G.R. VELLICCE, G. WESTERGAARD, M.G. GARCÍA, C.M.L. ROCHA, B. WELIN AND A.P. CASTAGNARO

Durban

Conferencia; World Soybean Conference South-Africa; 2013

Drought is one of the most important environmental stress in agriculture. The ability to produce high seed yield in drought affected fields is the ultimate indicator of drought tolerance (Du et al, 2009). However, genetics improvement for drought adaptation is largely addressed through the conventional approach of selecting for stable, high-yielding cultivars over varied locations and years (Babu et al, 2003). This approach is often very expensive, time consuming, and labor intensive, so the development of a reliable pot method for screen response to water stress in soybean genotypes under controlled or semi controlled conditions would allow identify genes involved in the response.A water stress of -0.65 MPa during 21 days was applied in reproductive stage R5. Total seed yield, total seed weight, 10-seed weight and total water consumption were measured and statistically analysed. Drought Susceptibility Index was calculated and three genotypes resulted tolerant (NA8000, PI416937 and Munasqa) and one susceptible (TJ2049). Samples from leaves were collected 72 h after water holding and RNA was purified for transcriptome analysis by 454 pyrosequencing (ROCHE). A total of 1,412,783 raw reads were obtained and assembled, by GS Reference Mapper software, into 18,219 high quality sequences. The average sequence length was 399 bp. All unique sequences were queried against Phytozome 7.0 Soybean database for annotation. Functional GO annotation was performed with sequences that produced significant hits with the MapMan Database. Informatics expression analysis identified 396 genes as typical from Munasqa, 846 from NA8000, 1099 from PI416937; while 487 were identified only in the susceptible TJ2049. A total of 1,157 genes were common to the three tolerant genotypes, 38 of them up regulated. Numerous genes were found to be over expressed in response to drought on tolerant genotypes while stay unchanged or repressed in the susceptible genotype. Other group of genes showed genotype specific changes; that lead to the suspect that different mechanisms are involved in their response to drought. This study represents the first large-scale transcriptomic analysis of soybean under drought stress in reproductive stage.