Abstract
ETO1 is a negative regulator of ethylene biosynthesis of Arabidopsis, that interacts with AtACS5. ETO1-transgenic tomato didn't show significant delay of fruit ripening, suggesting lack of sufficient interaction of ETO1 with endogenous ACSs in ripening fruit. ACSs were grouped into three types based on their C-terminal sequences. Y2H experiments showed that ETO1 failed to interact with LE-ACS2 (type 1) and LE-ACS4 (type 3), two major ACS isoforms in developing tomato fruit. On the other hand, auxin-inducible LE-ACS3 (type 2) interacted with ETO1, as well as AtACS5 (type 2). Chimeric construct between LE-ACS2 and LE-ACS3 revealed that the type 2-specific C-terminus is required for the interaction with ETO1. When treated with auxin, ETO1 transgenic seedling produced less amount of ethylene than wild type, despite induction of LE-ACS3 was comparable. These results suggest that ETO1 can regulate ethylene biosynthesis in heterologous plants and the regulation is specific for the type 2 ACSs.
