Transcriptional analysis of candidate genes involved in ABA and GA signalling during the expression and the termination of dormancy at different incubation thermal regimes in Sorghum bicolor (L. Moench) caryopses.

MENDIONDO, GUILLERMINA M.; RODRÍGUEZ, M. VERÓNICA; MASKIN, LAURA; BENECH-ARNOLD, R.L.

York

Workshop; 3rd International Workshop on the molecular aspects of seed dormancy and germination; 2010

ISSS (International Society for Seed Science)

Transcriptional analysis of candidate genes involved in ABA and GA signalling during the expression and the termination of dormancy at different incubation thermal regimes in Sorghum bicolor (L. Moench) caryopses. Guillermina M. Mendiondo1, María Verónica Rodríguez 1, Laura Maskin y Roberto Benech-Arnold 1 1IFEVA-Departamento de Producción Vegetal. Facultad de Agronomía, Universidad de Buenos Aires/CONICET. E-mail: mendion@agro.uba.ar   Germination of dormant sorghum grains can be promoted by incubating them under alternated temperatures (20/30ºC) or also at 30ºC constant. Alternating temperatures are thought to be a “dormancy terminating” factor, while high and constant temperatures are thought to affect only the “expression of dormancy”. The physiological and molecular basis of these two mechanisms was explored. Termination of dormancy by alternating temperatures was related to a decrease in embryo sensitivity to ABA (Benech-Arnold et al., 1995), while promotion of germination by high incubation temperatures is promoted by an increase in embryo sensitivity to GAs. Candidate genes involved in ABA and GA signalling were identified and expression analysis was done by RT-QPCR, embryos dissected from caryopses incubated at 20, 25, 30 or 20/30ºC. Comparative experiments were done using two inbred lines with contrasting patterns of dormancy release and preharvest sprouting behaviour. Embryonic ABA levels were also determined. Results show that expression of most ABA signalling candidate genes increased during incubation at 25ºC constant, while this increase was not observed under the 20/30ºC dormancy terminating regime. These results were confirmed at the protein level for ABI5 with specific antibodies. On the other hand, the effect of high constant incubation temperatures on the expression of dormancy was related to an increase in the expression of several GA signalling candidate genes but not to any evident modification in the expression of genes related to ABA signaling or GA metabolism. These results evince the different nature of the germination promoting effect of high incubation temperatures and alternating temperatures on dormant sorghum caryopses.