Bean class IV chitinase promoter is modulated during plant development and under abiotic stress

Abstract

To investigate howPvChi4promoter regulates gene expression during plant development and in response to stress, we have introduced promoter‐GUS transcriptional fusion constructs in transgenicArabidopsis thalianaand tobacco plants. GUS activity was not detected in aerial vegetative organs of transgenic plants carrying the 2189 bp promoter. However,gusexpression was activated at the parenchyma and epidermis of leaves and stem, when these transgenic tobacco plants were submitted to heat shock and UV irradiation. The non‐stressed plants showed promoter activity in the meristematic region of lateral roots and in reproductive organs. In both species, the promoter was active in pollen grains and ovaries. In tobacco anthers,gusexpression was observed in the middle layer. In transgenic plants harbouring promoters of 1445 bp, 1199 bp, 501 bp and 416 bp, GUS activity has been detected, in addition to the meristematic region of lateral roots, at the apical meristem, and in the phloem and epidermic tissues of leaves, stems and petioles. These analyses suggest that allcis‐acting elements controlling the tissue expression ofPvChi4promoter are located 416 bp upstream of the gene. A putative negative regulatory element that is inactivated during heat shock or UV treatments was also identified between 2189 and 1445 bp. GUS activity was not detected in globular embryos, but is present in the radicle region at the heart‐shaped stage. During transition from heart‐shaped to torpedo, the activity was extended until the hypocotyl. This expression pattern was maintained until embryo maturity, when staining was detected in the whole embryo, with lower intensity in the cotyledon region. These results corroborate the current idea that this class of chitinase may have some functional role on plant development in addition to the stress response.