AtMyb7, a subgroup 4 R2R3 Myb, negatively regulates ABA-induced inhibition of seed germination by blocking the expression of the bZIP transcription factor ABI5

Abstract

Various Myb proteins have been shown to play crucial roles in plants, including primary and secondary metabolism, determination of cell fate and identity, regulation of development and involvement in responses to biotic and abiotic stresses. The 126 R2R3 Myb proteins (with two Myb repeats) have been found in Arabidopsis; however, the functions of most of these proteins remain to be fully elucidated. In the present study, we characterized the function of AtMyb7 using molecular biological and genetic analyses. We used qRT-PCR to determine the levels of stress-response gene transcripts in wild-type and atmyb7 plants. We showed that ArabidopsisAtMyb7 plays a critical role in seed germination. Under abscisic acid (ABA) and high-salt stress conditions, atmyb7 plants showed a lower germination rate than did wild-type plants. Furthermore, AtMyb7 promoter:GUS seeds exhibited different expression patterns in response to variations in the seed imbibition period. AtMyb7 negatively controls the expression of the gene encoding bZIP transcription factor, ABI5, which is a key transcription factor in ABA signalling and serves as a crucial regulator of germination inhibition in Arabidopsis. Various Myb proteins have been shown to perform crucial roles in plants, including primary and secondary metabolism, regulation of cell fate and identity, regulation of development, and in the responses to biotic and abiotic stresses. Although 126 R2R3 Myb proteins (with 2 Myb repeats) have been found in Arabidopsis, a full understanding of the function of most of these proteins is lacking. We used molecular biological and genetic analyses to characterize the function of AtMyb7. qRT-PCR was used to determine the levels of stress response gene transcripts in wild-type and atmyb7 plants. We found that Arabidopsis AtMyb7 plays a critical role in seed germination. atmyb7 showed a lower germination rate than wild-type under high salt and abscisic acid (ABA) stress conditions. Furthermore, AtMyb7 pro-GUS seeds showed different expression patterns in response to variations in the seed imbibition period. AtMyb7 negatively controls the expression of the gene encoding the bZIP transcription factor ABI5, which is a key transcription factor in ABA signaling and serves as a crucial regulator of germination inhibition in Arabidopsis.