Functional studies of FIN219 gene expression in Arabidopsis
Date Issued
2004
Date
2004
Author(s)
Tseng, Mei-Hsuan
DOI
zh-TW
Abstract
After light irradiation, Plants are able to sense the changes of light environments by different photoreceptors, and then transduce the signal via light signaling components to regulate plant growth and development. fin219 mutant displays a long hypocotyl phenotype under continuous far red(cFR) light. The FIN219 gene has been isolated by map-based method and encodes a protein with 575 amino acids, which belongs to a GH3-like gene family in Arabidopsis. Furthermore, two coiled-coil domains, believed to be involved in protein-protein interaction, are found in FIN219 with one in the N-terminus and the other in the C-terminus. Currently, however, FIN219 function and regulatory mechanism are not clear yet and remain to be solved.
Transgenic plants overexpressing FIN219 or antisensing the N-terminus of FIN219 was used to study the effect of FIN219 on plant growth and development. Two different phenotypes of transgenic plants overexpressing the FIN219 grown in cFR were obtained, one with hypersensitive, shorter hypocotyl phenotype and the other with hyposensitive, longer hypocotyl phenotype than wild type. FIN219 expression in the shorter hypocotyls of transgenic plants grown in white light was investigated by Northern blot and found that it was indeed expressed more than that in wild type. However, its expression in the longer hypocotyls of transgenic plants didn’t show significant difference from that in wild type. Further, FIN219 protein expression in transgenic plants didn’t show significant difference when compared with wild type by Western blot analysis. In addition, transgenic plants antisensing the N-terminus of FIN219 exhibited intermediate hypocotyls in cFR compared to wild type and fin219 mutant. FIN219 mRNA level assayed by Northern was also reduced in some of the transgenic lines, but its protein level didn’t show obvious difference from wild type. Based on the results of these transgenic studies, it indicated that FIN219 acts as a positive regulator to transduce FR-mediated inhibition of hypocotyl elongation. Besides, the transgenic plants overexpressing FIN219 display a partial sterile flower phenotype, unequal size of asymmetric petals and spiral carpals. The antisense transgenic plants with lower level of FIN219 expression did show yellowish color of leaves, dwarf phenotype and a delayed flowering. That how the FIN219 affects all these phenotypes remains unclear.
To further understand regulatory mechanisms of FIN219 expression in light signaling, we investigate its expression in different light conditions and photomorphogenic mutants by western blotting. The results indicated that FIN219 protein was induced by cFR. FIN219 was also shown with different expression patterns in different cop1 alleles under dark and white light conditions. Furthermore, FIN219 protein expression was reduced in cry1 and cry2 mutants, and transgenic plants with FIN219 overexprssion also have a hypersensitive phenotype under blue light, implying that FIN219 may be involved in blue light signaling as well.
The result of promoter analysis by PLACE program indicated that there are several cold-activated cis-elements present in the promoter of FIN219 gene. Consistent with this, the result from cold-induced experiment showed that FIN219 mRNA expression detected by RT-PCR was reduced rapidly after cold treatment, then gradually increased up to 16 hours after cold treatment and then dropped again. However, FIN219 protein level did not change too much. In addition, FIN219 displays a tissue-specific manner with down-regulated in roots and reduced in the leaves of fin219 mutants compared to that in wild type. Interestingly, FIN219 exhibits two close sizes of bands with about 8 kD difference when detected by specific antibodies raised against the N-terminus of FIN219. The lower band will be shifted to the upper one after treated with phosphatase, suggesting that FIN219 protein may exist two forms to regulate plant growth and development.
Subjects
阿拉伯芥遠紅光訊息傳遞
phytochrome A
Type
other
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