DNA sequence variation of drought response candidate genes in Austrocedrus chilensis

POMPONIO, MAR¨ªA F.; TORALES, SUSANA; GALLO, LEONARDO ARIEL; MARCHELLI, PAULA; PASTORINO, MARIO JUAN; CERVERA, MAR¨ªA TERESA; MARCUCCI POLTRI, SUSANA

San Lorenzo de El Escorial

Conferencia; Evoltree Conference - Forest Ecosystem Genomics and Adaptation; 2010

Evoltree - INIA

Austrocedrus chilensis (D.Don) Pic. Ser. et Bizzarri, a native conifer of the Andean-Patagonian forest, is one of the several native tree species in Argentina that is characterized by a high adaptive growing potential in marginal areas and good technological timber quality. The large latitudinal and precipitation gradients that characterize the range of its geographical distribution (average annual rainfall from more than 2500 mm to less than 400 mm), lead us to analyze genetic adaptative variation at SNPs level in candidate genes involved in response to drought stress in the context of global warming. Information from partial or complete sequences of genes available in public databases from Pinus pinaster and P. taeda, Cryptomeria japonica, Prosopis juliflora and Arabidopsis were explored to design/select primers pair. Amplified heterologous fragments sequences from Aquaporin A and B, HAK3P, LP3-1 and  Pal 1were analyzed. DNA samples were collected from 30 trees coming from each of three areas with different precipitation regime: Llao Llao, Pedregoso, and San Ram¨®n. Twenty extra DNA samples from drought stress assays also were included for the analysis. About 716 sequences (sequenced in both directions) were obtained mainly from Pal 1, Aquaporin A and B genes harbouring 600, 300 y 250 bp respectively. We found a high rate of  SNPs, being in average one SNP per 19 bp across coding and noncoding regions. Aquaporin genes showed the largest number of SNPs, meanwhile Pal 1 amplified fragments presented only a few. Moderate average nucleotide diversity (¦Ð) of 0.00922 for pooled samples was found varying 100-fold among single genes. Several neutrality tests were performed to identify candidate genes that might be under natural selection. Four genes resulted in negative values, being Aquaporin A and LP3-1 the only ones statistically significant. Also, the non-synonymous/synonymous mutation rate was estimated, showing values below 1,  suggesting divergence from neutrality. Possible causes we will discussed. This is the first report on SNPs variation in genes potentially involved in drought response in natural populations of Austrocedrus chilensis, a cypress of the Andean-Patagonian Forest. The discovered polymorphism will be used for further evaluation of the adaptive role of genes through association mapping.