Department of Biology, Faculty of science, Islamic University in Madinah, Madinah, Saudi Arabia,
Appl Biochem Biotechnol. 2014 Mar;172(5):2480-95. doi: 10.1007/s12010-013-0710-4. Epub 2014 Jan 8.
Plant proteome databases were mined for a flavin monooxygenase (YUCCA), tryptophan decarboxylase (TDC), nitrilase (NIT), and aldehyde oxidase (AO) enzymes that could be involved in the tryptophan-dependent pathway of auxin biosynthesis. Phylogenetic trees for enzyme sequences obtained were constructed. The YUCCA and TDC trees showed that these enzymes were conserved across the plant kingdom and therefore could be involved in auxin synthesis. YUCCAs branched into two clades. Most experimentally studied YUCCAs were found in the first clade. The second clade which has representatives from only seed plants contained Arabidopsis sequences linked to embryonic development. Therefore, sequences in this clade were suggested to be evolved with seed development. Examination of TDC activity and expression had previously linked this enzyme to secondary products synthesis. However, the phylogenetic finding of a conserved TDC clade across land plants suggested its essential role in plant growth. Phylogenetic analysis of AOs showed that plants inherited one AO. Recent gene duplication was suggested as AO sequences from each species were similar to each other rather than to AO from other species. Taken together and based on the experimental support of the involvement of AO in abscisic synthesis, AO was excluded as an intermediate in IAA production. Phylogenetic tree for NIT showed that the first clade contained sequences from species across the plant kingdom whereas the second branch contained sequences from only Brassicaceae. Even though NIT4 orthologues were conserved in the second clade, their major role seems to be detoxification of hydrogen cyanide rather than producing IAA.
植物蛋白质组数据库中挖掘了黄素单加氧酶（YUCCA）、色氨酸脱羧酶（TDC）、腈酶（NIT）和醛氧化酶（AO）等可能参与生长素生物合成色氨酸依赖途径的酶。构建了获得的酶序列的系统发育树。YUCCA 和 TDC 树表明，这些酶在植物界中是保守的，因此可能参与生长素合成。YUCCAs 分为两个分支。大多数经过实验研究的 YUCCAs 都存在于第一个分支中。第二个分支仅包含来自种子植物的代表，其中包含与胚胎发育相关的拟南芥序列。因此，该分支中的序列被认为是与种子发育一起进化的。TDC 活性和表达的检测先前将该酶与次生产物合成联系起来。然而，陆地植物中保守 TDC 分支的系统发育发现表明其在植物生长中具有重要作用。AO 的系统发育分析表明，植物遗传了一个 AO。最近的基因复制被认为是由于每个物种的 AO 序列彼此相似，而不是与其他物种的 AO 相似。综合考虑并基于 AO 参与脱落酸合成的实验支持，AO 被排除在 IAA 产生的中间产物之外。NIT 的系统发育树表明，第一个分支包含来自植物界各个物种的序列，而第二个分支仅包含来自十字花科的序列。尽管第二分支中保守了 NIT4 同源物，但它们的主要作用似乎是解毒氢氰酸，而不是产生 IAA。
