Vacuolar H+-ATPase is expressed in response to gibberellin during tomato seed germination

Completion of germination (radicle emergence) by gibberellin (GA)-deficient (gib-1) mutant tomato (Lycopersicon esculentum Mill.) seeds is dependent u pon exogenous GA, because weakening of the endosperm tissue enclosing the r adicle tip requires GA. To investigate genes that may be involved in endosp erm weakening or embryo growth, differential cDNA display was used to ident ify mRNAs differentially expressed in gib-1 seeds imbibed in the presence o r absence of GA(4+7). Among these was a GA-responsive mRNA encoding the 16- kD hydrophobic subunit c of the V-0 membrane sector of vacuolar H+-transloc ating ATPases (V-ATPase), which we termed LVA-P1. LVA-P1 mRNA expression in gib-1 seeds was dependent on GA and was particularly abundant in the micro pylar region prior to radicle emergence. Both GA dependence and tissue loca lization of LVA-P1 mRNA expression were confirmed directly in individual gi b-1 seeds using tissue printing. LVA-P1 mRNA was also expressed in wild-typ e seeds during development and germination, independent of exogenous GA. Sp ecific antisera detected protein subunits A and B of the cytoplasmic V-1 se ctor of the V-ATPase holoenzyme complex in gib-1 seeds only in the presence of GA, and expression was localized to the micropylar region. The results suggest that V-ATPase plays a role in GA-regulated germination of tomato se eds.