In vitro binding of Sorghum bicolor transcription factors ABI4 and ABI5 to a conserved region of a GA 2 - OXIDASE promoter possible role of this interaction in the expression of seed dormancy
The precise adjustment of the timing of dormancy release according to final grain usage is still a challenge for many cereal crops. Grain sorghum [Sorghum bicolor [L.] Moench] shows wide intraspecific variability in dormancy level and susceptibility to pre-harvest sprouting [PHS]. Both embryo sensitivity to abscisic acid [ABA] and gibberellin [GA] metabolism play an important role in the expression of dormancy of the developing sorghum grain. In previous works, it was shown that, simultaneously with a greater embryo sensitivity to ABA and higher expression of SbABA-INSENSITIVE 4 [SbABI4] and SbABA-INSENSITIVE 5 [SbABI5], dormant grains accumulate less active GA4 due to a more active GA catabolism. In this work, it is demonstrated that the ABA signalling components SbABI4 and SbABI5 interact in vitro with a fragment of the SbGA 2-OXIDASE 3 [SbGA2ox3] promoter containing an ABA-responsive complex [ABRC]. Both transcription factors were able to bind the promoter, although not simultaneously, suggesting that they might compete for the same cis-acting regulatory sequences. A biological role for these interactions in the expression of dormancy of sorghum grains is proposed: either SbABI4 and/or SbABI5 activate transcription of the SbGA2ox3 gene in vivo and promote SbGA2ox3 protein accumulation; this would result in active degradation of GA4, thus preventing germination of dormant grains. A comparative analysis of the 5'-regulatory region of GA2oxs from both monocots and dicots is also presented; conservation of the ABRC in closely related GA2oxs from Brachypodium distachyon and rice suggest that these species might share the same regulatory mechanism as proposed for grain sorghum.
| Main Authors: | , , , |
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| Format: | Texto biblioteca |
| Language: | eng |
| Subjects: | ABI4, ABI5, ABSCISIC ACID, GA 2-OXIDASE, GERMINATION, GIBBERELLINS, SEED DORMANCY, SORGHUM BICOLOR, |
| Online Access: | http://ceiba.agro.uba.ar/cgi-bin/koha/opac-detail.pl?biblionumber=46879 |
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