Functional analysis of four genes in regulating flower organ senescence and abscission in Arabidopsis thaliana

• Main Authors: Jou-Chen Wang, 汪柔辰
• Other Authors: Chang-Hsien Yang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/92366867891141973873

碩士 === 國立中興大學 === 生物科技學研究所 === 102 === (1)FYF has been thought to play a repressor role in controlling flower senescence/abscission. In this study, three Ethylene-Responsive Factor (ERF) genes, FYF ACTIVATING FACTOR 2 (FAF2/ERF19) , ERF87, ERF91, up-regulated by FYF were identified from microarray analysis. Ectopic expression of FAF2 delayed flower senescence/abscission and produced more flowers on inflorescence. Further confocol microscopy analysis found that the size of shoot apical meristem in 35S::FAF2 is bigger than that in wild-type and the number of flower buds is also more than that in wild-type. The production of more flowers in 35S::FAF2 was found due to the up-regulation of shoot apical meristem activity determined gene WUS, a similar effect caused by the activation of plant hormone cytokinin. Since the expression level of cytokinin synthesis and signal transduction related genes was not affected in 35S::FAF2 transgenic plants, we used microarray to analyze the putative downstream regulation pathway of FAF2. The result shows that FAF2 probably reduced auxin contents by inhibiting auxin biosynthesis genes MYB51, CYP79B2 and CYP71A13 to promote the expression of WUS gene. It also shows that FAF2 may regulate flower senescence by down-regulated jasmonate or ethylene signal transduction genes ORA47, ORA59, RAP2.6, WRKY33, WRKY38, WRKY40, WRKY53 and WRKY70. We proposed that FAF2 may regulate the WUS gene by down-regulating IAA biosynthesis or jasmonate signal transduction to affect shoot apical meristem activity. In this study, two other ERF genes, ERF87 and 91, up-regulated by FYF in 35S::FYF transgenic plant, were also characterized. The expression of ERF87 and 91 were decreased in mature flower and was up-regulated by 35S::FYF. Ectopic expression of ERF87 and ERF87-VP16 inhibited root development and delayed flowering by inhibiting FT expression. Ectopic expression of ERF87-VP16 also caused leaf incurvature by actitviting AS1 and AS2 gene expression and produced more trichome by promoting MYB75 and GL3. Furthermore, 35S::ERF87-VP16 also inhibited petal and sepal growth by down-regulating MYB21, MYB24 and MYB57 to inhibit cell division and expansion. By contrast, 35S::ERF87-SRDX showed the opposite phenotype to 35S::ERF87 by promoting flowering and the growth and the development of root and flower organs. These results indicate that ERF87 plays as an activator to regulate flower development. In addition, ectopic expression of ERF91 and ERF91-VP16 delayed flowering by suppressing FT expression whereas ERF91-SRDX promoted flowering. This data shows that ERF91 functions as an activator to regulate flowering. In summary, ERF87 and ERF91 were up-regulated by FYF to involve in flower development but not in senescence and abscission. Flowering is controlled by several environmental signals such as photoperiodic, autonomous, vernalization and GA pathway. In the photoperiodic pathway, the circadian-regulated gene CONSTANS (CO) plays an important role to regulate the flowering in Arabidopsis, CO protein is able to promote the flowering through the activation of the downstream gene FT. In addition to CO gene, there are 16 other COLs genes belonging to CO/COL family. COL3 which belongs to the same subgroup with CO has been cloned for functional analysis. It has been found that COL3 could involve in the regulation of flowering time, flower senescence/abscission and salt tolerance. This study further analyzed the mechanisms of COL3 in regulating plant growth development. COL3 expressed in shoot apical meristem, cotelodon, true leave and root of 7-day and 14-day-old seedlings. The expression of COL3 was higer in mature flower than in flower buds. In flowers, COL3 expressed in sepals and filament of mature flower as well as in silique. Ectopic expression of COL3, COL3-SRDX, COL3-VP16 promoted flowering by activating FT gene. Ectopic expression of COL3 and COL3-SRDX also caused early flower senescence by activating ethylene signal transduction genes EDF1 and EDF4, and also promoted abscission by activating abscission-associated genes HSL and HAESA. Furthermore, ectopic expression COL3-SRDX produced short flower organs by suppressing jasmonate signal transduction genes MYB21, MYB24 and MYB57. These results suggest a possible repressor role for COL3 in controlling flower senescence and abscission.