ObjectiveCurrently, researches on the gene function of plant SPL8 are mainly focused on flowering and fertility, but there are fewer reports about its SPL8 function in drought stress response. In this paper, BpSPL8 promoter was cloned and analyzed from Betula platyphylla, and the function of BpSPL8 gene in response to drought stress was studied in Arabidopsis thaliana.
MethodPromoter sequence of BpSPL8 gene was isolated from Betula platyphylla by PCR technology, and the cis-element prediction of BpSPL8 promoter was performed using PLACE and PlantCARE software. The plant expression vectors with GUS (β-glucuronidase coding gene) expression driven by the promoters of BpSPL8 were constructed and transformed into Arabidopsis thaliana by the floral dip method. Through the detection of GUS activity, the tissue expression pattern of the BpSPL8 promoter in Arabidopsis thaliana was analyzed. QRT-PCR analysis was performed on the expression level of BpSPL8 under PEG treatment. Finally, the overexpression of BpSPL8 Arabidopsis thaliana was used to explore the function of BpSPL8 in the drought process.
ResultPromoter element analysis revealed that BpSPL8 promoter contained elements for tissue-specific expression, light-responsive, hormone-responsive and stress-responsive. GUS histochemical staining results showed that GUS activity was observed in hypocotyls, leaves, petioles, roots and inflorescences of transgenic Arabidopsis thaliana carrying the BpSPL8 promoter. The expression patterns of BpSPL8 gene in roots and leaves of birch were up-regulated and then down-regulated under PEG treatment. Drought stress tolerance pointed out that the transgenic plants showed significantly lower survival rate and proline content than wild type, while malondialdehyde content was higher than wild type. Two known stress-resistant genes, DR29B and P5CS1, were up-regulated in wild-type and transgenic Arabidopsis thaliana under drought stress. However, compared with wild-type, they showed delayed up-regulation in transgenic Arabidopsis thaliana.
ConclusionEctopic overexpression of BpSPL8 can reduce the drought tolerance of Arabidopsis thaliana and affect the expression patterns of resistance genes DR29B and P5CS1 under drought stress.