中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
2beta,3beta,4aalpha-三羟基-1beta-甲基-8-亚甲基赤霉素烷-1alpha,10beta-二甲酸1,4alpha-内酯 | gibberellin A34 | 32630-92-5 | C19H24O6 | 348.396 |
Arabidopsis thaliana GAMT1 and GAMT2 encode enzymes that catalyze formation of the methyl esters of gibberellins (GAs). Ectopic expression of GAMT1 or GAMT2 in Arabidopsis, tobacco (Nicotiana tabacum), and petunia (Petunia hybrida) resulted in plants with GA deficiency and typical GA deficiency phenotypes, such as dwarfism and reduced fertility. GAMT1 and GAMT2 are both expressed mainly in whole siliques (including seeds), with peak transcript levels from the middle until the end of silique development. Within whole siliques, GAMT2 was previously shown to be expressed mostly in developing seeds, and we show here that GAMT1 expression is also localized mostly to seed, suggesting a role in seed development. Siliques of null single GAMT1 and GAMT2 mutants accumulated high levels of various GAs, with particularly high levels of GA1 in the double mutant. Methylated GAs were not detected in wild-type siliques, suggesting that methylation of GAs by GAMT1 and GAMT2 serves to deactivate GAs and initiate their degradation as the seeds mature. Seeds of homozygous GAMT1 and GAMT2 null mutants showed reduced inhibition of germination, compared with the wild type, when placed on plates containing the GA biosynthesis inhibitor ancymidol, with the double mutant showing the least inhibition. These results suggest that the mature mutant seeds contained higher levels of active GAs than wild-type seeds.
拟南芥GAMT1和GAMT2编码催化赤霉素(GAs)的甲酯形成的酶。在拟南芥、烟草(Nicotiana tabacum)和矮牵牛(Petunia hybrida)中外源表达GAMT1或GAMT2导致植物缺乏GA和典型的GA缺乏表型,如侏儒和生育力降低。GAMT1和GAMT2主要在整个角果(包括种子)中表达,峰值转录水平从角果发育的中期到末期。在整个角果中,GAMT2先前被证明主要在发育的种子中表达,我们在这里显示GAMT1表达也主要定位于种子,暗示其在种子发育中的作用。单个GAMT1和GAMT2突变体的角果积累了各种GAs的高水平,双突变体中GA1的水平尤为高。野生型角果中未检测到甲基化GAs,表明GAMT1和GAMT2对GAs的甲基化作用是使GAs失活并在种子成熟时启动其降解。当放置在含有GA生物合成抑制剂ancymidol的培养皿上时,纯合GAMT1和GAMT2缺失突变体的种子与野生型相比表现出较少的萌发抑制,双突变体的抑制最少。这些结果表明,成熟的突变体种子中含有比野生型种子更高水平的活性GAs。