A novel Arabidopsis BHLH transcription factor regulates seed germination antagonizing ABA-signaling

MORENO-PIOVANO, GS; MORENO, JE; CHAN, RL

Rosario

Congreso; SAIB 2014; 2014

Seed germination is influenced by a myriad set of abiotic factors. Soil salinity is a potent inhibitor of this process in which the hormone abscicic acid (ABA) plays a central role. Here, we present a characterization of a basic/helix-loophelix (bHLH) transcription factor related to the ABA signaling pathway during germination. Following a reverse genetic assay, we used a set of bhlhX T-DNA Arabidopsis insertional mutants to test the germination rate in the presence of ABA or salt (NaCl). Among the mutant lines, one showed enhanced inhibition of the germination rate in the presence of increasing concentrations of NaCl compared to WT seeds. Concomitantly, this mutant also exhibited an increased sensitivity to ABA during germination, as well as a higher dormancy rate when germinated on soil. To underscore the physiological mechanisms behind this transcription factor, we performed a phenotype comparison between the bhlh mutant and known ABA signaling mutants. The abi4 mutant, defective in the ABI4 transcription factor with diverse roles in ABA responses, displayed an opposite set of characteristics including viviparism, ABA and salt insensitivity. Interestingly, the bhlh mutant showed increased expression of ABI4. We propose a model in which bHLH and ABI4 regulate each other in an antagonistic manner to modulate the germination rate upon challenging environmental conditions.