Dominant And Pleiotropic Effects Of A GAI Gene In Wheat Results From Lack Of Interaction Between DELLA And GID1

Dominance, semidominance and recessiveness are important modes of Mendelian inheritance. The phytohormone gibberellin (GA) regulates many plant growths and developmental processes. The previously cloned semidominant GAI (GA-insensitive) genes Rhtl and Rht2in wheat were the basis of the 'green revolution'. However, no completely dominant GAI gene has been cloned. Here, we report molecular characterization of Rht-Blc, a dominant GAI allele in wheat, which confers more extreme characteristics than its incompletely dominant alleles.The results obtained are as follows:1. It is the first cloning unique dwarfing gene of China, Rht-Blc, which is caused by a TRIM (terminal repeat retro-transposons in miniature) insertion in the DELL A domain.2. We analyzed Rht-Blc functions using near-isogenic lines (NILs), and examined its molecular mechanisms in transgenic rice, and its effects were even more extreme than in wheat.3. Yeast two-hybrid (Y2H) assays showed that Rht-Blc protein fails to interact with GID1, thereby blocking GA responses and resulting in extreme dwarfism and pleiotropic effects. By contrast Rht-Blb protein only reduces interaction with GID1.4. These results indicated that the affinity between GID1and DELLA proteins is key regulation of the stability of DELLA proteins, and differential interactions determine dominant and semidominant gene action responded to GA.