Induction of isoforms of tetrapyrrole biosynthetic enzymes, AtHEMA2 and AtFC1, under stress conditions and their physiological functions in arabidopsis
Induction of isoforms of tetrapyrrole biosynthetic enzymes, AtHEMA2 and AtFC1, under stress conditions and their physiological functions in arabidopsis
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DOI：
10.1104/pp.107.100065
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发表时间：
2007-06-01
期刊：
影响因子：
7.4
通讯作者：
Masuda, Tatsuru
中科院分区：
文献类型：
--
作者：
Nagai, Satoshi;Koide, Masumi;Masuda, Tatsuru
在四吡咯生物合成途径中，谷氨酰-tRNA还原酶（HEMA 2）和亚铁螯合酶1（FC 1）的亚型主要在非光合组织中表达。在这里，使用启动子-β-葡萄糖醛酸苷酶构建体，我们表明，拟南芥（拟南芥）HEMA 2（AtHEMA 2）和FC 1（AtFC 1）的表达诱导光合组织的氧化应激，如创伤。转录水平和β-葡萄糖醛酸酶活性在30分钟内迅速诱导，特别是在伤口区域以茉莉酸盐非依赖性方式。创伤特异性早期诱导基因的转录组分析表明，AtHEMA 2和AtFC 1与质体外的血红素蛋白共诱导，这与防御反应有关。臭氧熏蒸或产生活性氧的试剂诱导光合组织中这两个基因的表达，表明活性氧参与了诱导。由于放线菌酮或嘌呤霉素诱导这两个基因的表达，抑制胞质蛋白质合成参与这些基因在光合组织中的诱导。AtHEMA 2和AtFC 1的生理功能进行了研究，使用每个基因的插入敲除突变体。血红素含量的两个突变体的根约为各自的野生型的一半。在野生型植物中，血红素含量增加臭氧暴露。在这两个突变体中，臭氧诱导的血红素含量的增加减少。这些结果表明，AtHEMA 2和AtFC 1，这通常在非光合组织中的血红素生物合成的功能控制的四吡咯生物合成途径的存在，但诱导在光合组织在氧化条件下供应血红素防御性血红素蛋白质外质体。
In the tetrapyrrole biosynthetic pathway, isoforms of glutamyl-tRNA reductase (HEMA2) and ferrochelatase1 (FC1) are mainly expressed in nonphotosynthetic tissues. Here, using promoter-beta-glucuronidase constructs, we showed that the expressions of Arabidopsis (Arabidopsis thaliana) HEMA2 (AtHEMA2) and FC1 (AtFC1) were induced in photosynthetic tissues by oxidative stresses such as wounding. Transcript levels and beta-glucronidase activity were rapidly induced within 30 min, specifically in the wound area in a jasmonate-independent manner. Transcriptome analysis of wound-specific early inducible genes showed that AtHEMA2 and AtFC1 were coinduced with hemoproteins outside plastids, which are related to defense responses. Ozone fumigation or reagents generating reactive oxygen species induced the expression of both genes in photosynthetic tissues, suggesting that reactive oxygen species is involved in the induction. Since cycloheximide or puromycin induced the expression of both genes, inhibition of cytosolic protein synthesis is involved in the induction of these genes in photosynthetic tissues. The physiological functions of AtHEMA2 and AtFC1 were investigated using insertional knockout mutants of each gene. Heme contents of the roots of both mutants were about half of that of the respective wild types. In wild-type plants, heme contents were increased by ozone exposure. In both mutants, reduction of the ozone-induced increase in heme content was observed. These results suggest the existence of the tetrapyrrole biosynthetic pathway controlled by AtHEMA2 and AtFC1, which normally functions for heme biosynthesis in nonphotosynthetic tissues, but is induced in photosynthetic tissues under oxidative conditions to supply heme for defensive hemoproteins outside plastids.