CONICET | Buscador de Institutos y Recursos Humanos

Interaction between ABA signaling and GA metabolism in sorghum lines with contrasting sprouting behavior Ma. Verónica Rodríguez, Guillermina M. Mendiondo and Roberto L. Benech-Arnold IFEVA - Cátedra de Cerealicultura, Facultad de Agronomía de la Universidad de Buenos Aires. Av. San Martín 4453 (C1417DSE) Buenos Aires, Argentina. mvr@agro.uba.ar Expression of seed dormancy in imbibed sorghum (S.bicolor (L) Moench) grains is regulated by the counteracting effects of abscisic acid (ABA) and gibberellins (GAs). In previous works we have shown that ABA signaling is stronger during incubation of IS9530 grains, a line with a long lasting dormancy and sprouting resistant, as compared to RedlandB2, a line that loses dormancy precociously and is susceptible to pre-harvest sprouting. Expression analysis of several genes involved in ABA signaling (SbABI5, SbABI4, SbVP1, SbABI1, SbPKABA1, etc) in both lines showed that these genes reached higher expression levels in dormant IS9530 grains and this was in accordance with the stronger sensitivity to the inhibitory effect of ABA observed for this genotype. We also addressed a possible interaction between ABA signaling and GA metabolism; we present results showing that the incubation of isolated embryos in presence of 50uM ABA inhibited germination and endogenous GA levels were also significantly reduced as compared to embryos incubated in water (which germinate completely). Down-regulation of GA levels both in IS9530 grains and also during incubation in ABA was associated to a stronger expression of a GA2-oxidase gene, involved in GA inactivation. Our current efforts are directed to studying a possible interaction between transcription factors involved in ABA signaling and the promoter of the GA2-oxidase gene. The sequence of the GA2-oxidase promoter includes several cis-elements related to ABA signaling, such as ABRE and RY repeats.