Plant Biochemistry Laboratory, Department of Plant Biology and Biotechnology, University of Copenhagen, 40 Thorvaldsensvej, Frederiksberg C, Copenhagen, Denmark.
Mol Plant. 2010 Jan;3(1):192-211. doi: 10.1093/mp/ssp098. Epub 2009 Dec 14.
Auxin homeostasis is pivotal for normal plant growth and development. The superroot2 (sur2) mutant was initially isolated in a forward genetic screen for auxin overproducers, and SUR2 was suggested to control auxin conjugation and thereby regulate auxin homeostasis. However, the phenotype was not uniform and could not be described as a pure high auxin phenotype, indicating that knockout of CYP83B1 has multiple effects. Subsequently, SUR2 was identified as CYP83B1, a cytochrome P450 positioned at the metabolic branch point between auxin and indole glucosinolate metabolism. To investigate concomitant global alterations triggered by knockout of CYP83B1 and the countermeasures chosen by the mutant to cope with hormonal and metabolic imbalances, 10-day-old mutant seedlings were characterized with respect to their transcriptome and metabolome profiles. Here, we report a global analysis of the sur2 mutant by the use of a combined transcriptomic and metabolomic approach revealing pronounced effects on several metabolic grids including the intersection between secondary metabolism, cell wall turnover, hormone metabolism, and stress responses. Metabolic and transcriptional cross-talks in sur2 were found to be regulated by complex interactions between both positively and negatively acting transcription factors. The complex phenotype of sur2 may thus not only be assigned to elevated levels of auxin, but also to ethylene and abscisic acid responses as well as drought responses in the absence of a water deficiency. The delicate balance between these signals explains why minute changes in growth conditions may result in the non-uniform phenotype. The large phenotypic variation observed between and within the different surveys may be reconciled by the complex and intricate hormonal balances in sur2 seedlings decoded in this study.
生长素稳态对于植物正常生长和发育至关重要。超级根 2 （sur2）突变体最初是在生长素过表达的正向遗传筛选中分离出来的，并且 SUR2 被认为控制生长素缀合，从而调节生长素稳态。然而，表型并不一致，不能描述为纯高生长素表型，这表明 CYP83B1 的敲除具有多种效应。随后，SUR2 被鉴定为 CYP83B1，一种位于生长素和吲哚葡萄糖苷代谢分支点的细胞色素 P450。为了研究 CYP83B1 敲除引发的伴随全局变化以及突变体选择应对激素和代谢失衡的对策，对 10 天大的突变体幼苗的转录组和代谢组谱进行了特征分析。在这里，我们通过使用组合转录组学和代谢组学方法对 sur2 突变体进行了全面分析，揭示了对几个代谢网格的明显影响，包括次生代谢、细胞壁周转、激素代谢和应激反应的交叉。发现 sur2 中的代谢和转录交叉是由正、负作用转录因子之间的复杂相互作用调节的。因此，sur2 的复杂表型不仅归因于生长素水平升高，还归因于乙烯和脱落酸反应以及在没有水分缺乏的情况下的干旱反应。这些信号之间的微妙平衡解释了为什么生长条件的微小变化可能导致非均匀表型。在不同调查之间和之内观察到的大表型变异可以通过本研究中解码的 sur2 幼苗中复杂而复杂的激素平衡来协调。
