Differential expression of acid invertase genes during seed germination in Arabidopsis thaliana

In Arabidopsis thaliana (L.) Heynh ecotype Landsberg, levels of soluble acid invertase activity are closely related to the progress of seed germination. To study the mechanism(s) of the development of these enzymes, two cDNA clones that encode putative vacuolar acid invertases were isolated from germinating seeds and very young seedlings using reverse-transcription polymerase chain reactions with degenerate primers. These fragments corresponded to the genes At betafruct3 and At betafruct4 from the Columbia ecotype. An apoplasmic invertase gene corresponding to At betafruct1/ATCWINV1 was also isolated from these samples. Northern blot analyses showed that A tbetafruct3 and Atflfruc4 are expressed concomitantly with germination and the subsequent seedling growth. In contrast, the At betaflfruct1/ AtcwINV1 mRNA is translated before germination. These expression patterns are regulated by phytochrome, which perceives red light and in turn triggers de novo synthesis of gibberellin, initiating Arabidopsis seed germination. To test the effects of gibberellin on the expression of these genes, seed were treated with a gibberellin biosynthesis inhibitor, uniconazole or pro-hexadione. These chemicals inhibited both seed germination and expression of the above genes, but subsequently applied GA(4), an active gibberellin, reversed the inhibition. These results suggest that the transcription of genes encoding the vacuolar invertases, At betafruct3 and At betafruct4 and a gene encoding the apoplasmic invertase, At betafruct1/AtcwINV1, are induced by gibberellin synthesized de novo following irradiation with red light.