Natural variations in the promoter of a vacuolar invertase gene from Elsholtzia haichowensis lead to different responses to glucose

Invertases hydrolyze sucrose and play crucial roles in plant growth and development as well as defense responses to stresses. However, little is known about the molecular basis controlling invertase gene regulation under stresses. Our previous study has shown that the expression of a vacuolar invertase gene, EhvINVMP, in roots of a metalliferous population of Elsholtzia haichowensis was induced under Cu stress, whereas the expression of EhvINVNMP, an allele from a non-metalliferous population, was not affected. Here, we cloned the promoters of EhvINVNMP and EhvINVMP and found 12 % sequence divergence between them. The promoters of both alleles drive GUS expression in roots, leaves, stems, flowers and seeds of transgenic Arabidopsis thaliana with preferences for the vascular tissues. GUS activities conferred by the two promoters were not responsive to Cu stress, drought, IAA, 6-BA, ABA, ACC, MeJA and SA in transgenic A. thaliana, but were induced by GA3. The promoter activity and expression of EhvINVMP were induced by glucose while those of EhvINVNMP were not affected. Deletion analysis of the pEhvINVMP promoter showed that a 40 bp insertion sequence containing a SP8b and a SURE2-like AATACTAT element might be responsible for its glucose induction. The glucose-induction of EhvINVMP provides a positive feed-forward mechanism to maintain and amplify the induction of EhvINVMP by Cu stress, thus might explaining the different regulation of EhvINVNMP and EhvINVMP under Cu stress. Our study provides new insight into the regulation of invertase gene under stresses.

Automated summary

This study reveals that the promoter activity and expression of EhvINVMP, a vacuolar invertase gene, are induced by glucose and Cu stress, while those of EhvINVNMP, an allele from a non-metalliferous population, are not affected. The glucose induction of EhvINVMP provides a positive feed-forward mechanism to amplify its induction by Cu stress, explaining the different regulation of EhvINVNMP and EhvINVMP under Cu stress.