Transcriptional feedback regulation of YUCCA genes in response to auxin levels in Arabidopsis
Transcriptional feedback regulation of YUCCA genes in response to auxin levels in Arabidopsis
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DOI：
10.1007/s00299-015-1791-z
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发表时间：
2015-08-01
影响因子：
6.2
通讯作者：
Shimada, Yukihisa
中科院分区：
文献类型：
--
作者：
Suzuki, Masashi;Yamazaki, Chiaki;Shimada, Yukihisa
IPyA 途径是主要的生长素生物合成途径，通过响应活性生长素水平的负反馈机制进行转录调节。植物激素生长素在植物生长和发育中发挥重要作用，活性游离生长素的水平由生物合成、结合和极性运输决定。与缀合和极性运输不同，人们对生长素生物合成的调节机制知之甚少。我们发现，编码吲哚-3-丙酮酸（IPyA）途径酶的基因的表达受活性生长素水平升高或降低的调节。 TAR2、YUC1、YUC2、YUC4 和 YUC6 的表达水平因外源应用于拟南芥幼苗的合成生长素 [1-萘乙酸 (NAA) 和 2,4-二氯苯氧基乙酸 (2,4-D)] 而下调。与此同时，观察到内源性吲哚-3-乙酸 (IAA) 水平降低。或者，在拟南芥幼苗中，生长素生物合成抑制剂犬尿氨酸上调了这些 YUCCA 基因的表达，同时 IAA 水平降低。这些结果表明YUCCA基因的表达受到活性生长素水平的调节。在生长素过量产生和生长素缺乏的突变体中也观察到类似的结果。与仅暴露于 IPyA 的幼苗相比，对用犬尿氨酸预培养的拟南芥幼苗施加外源 IPyA 增加了内源 IAA 水平，而用 2,4-D 预培养则降低了内源 IAA 水平。这些结果表明，在生长素水平降低的情况下IPyA向IAA的体内转化增强，而在过量的生长素存在下IPyA向IAA的转化受到抑制。基于这些结果，我们提出 IPyA 途径通过响应活性生长素水平的负反馈机制进行转录调节。
The IPyA pathway, the major auxin biosynthesis pathway, is transcriptionally regulated through a negative feedback mechanism in response to active auxin levels.The phytohormone auxin plays an important role in plant growth and development, and levels of active free auxin are determined by biosynthesis, conjugation, and polar transport. Unlike conjugation and polar transport, little is known regarding the regulatory mechanism of auxin biosynthesis. We discovered that expression of genes encoding indole-3-pyruvic acid (IPyA) pathway enzymes is regulated by elevated or reduced active auxin levels. Expression levels of TAR2, YUC1, YUC2, YUC4, and YUC6 were downregulated in response to synthetic auxins [1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D)] exogenously applied to Arabidopsis thaliana L. seedlings. Concomitantly, reduced levels of endogenous indole-3-acetic acid (IAA) were observed. Alternatively, expression of these YUCCA genes was upregulated by the auxin biosynthetic inhibitor kynurenine in Arabidopsis seedlings, accompanied by reduced IAA levels. These results indicate that expression of YUCCA genes is regulated by active auxin levels. Similar results were also observed in auxin-overproduction and auxin-deficient mutants. Exogenous application of IPyA to Arabidopsis seedlings preincubated with kynurenine increased endogenous IAA levels, while preincubation with 2,4-D reduced endogenous IAA levels compared to seedlings exposed only to IPyA. These results suggest that in vivo conversion of IPyA to IAA was enhanced under reduced auxin levels, while IPyA to IAA conversion was depressed in the presence of excess auxin. Based on these results, we propose that the IPyA pathway is transcriptionally regulated through a negative feedback mechanism in response to active auxin levels.