Transcripts of two ent-copalyl diphosphate synthase genes differentially localize in rice plants according to their distinct biological roles.
Transcripts of two ent-copalyl diphosphate synthase genes differentially localize in rice plants according to their distinct biological roles.
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DOI：
10.1093/jxb/eru424
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发表时间：
2015-01
影响因子：
6.9
通讯作者：
Yamane H
中科院分区：
文献类型：
--
作者：
Toyomasu T;Usui M;Sugawara C;Kanno Y;Sakai A;Takahashi H;Nakazono M;Kuroda M;Miyamoto K;Morimoto Y;Mitsuhashi W;Okada K;Yamaguchi S;Yamane H
用于赤霉素生物合成的二萜合酶基因的表达发生在与其用于植物抗毒素生物合成的同种型表达的组织不同的组织中，反映了它们在水稻中不同的生物学作用。赤霉素（GAs）是调节植物生长的多个方面的二萜类植物激素。四环烃对映贝壳杉烯（ent-kaurene）是天然气生物合成的中间体，由二萜类化合物的前体香叶基香叶基二磷酸（geranylgeranyldiphosphate）经对映柯巴基二磷酸（ent-copalyl diphosphate，ent-CDP）合成酶和对映贝壳杉烯合成酶催化环化反应生成。水稻（Oryza sativa L.）具有两个ent-CDP合酶基因OsCPS 1和OsCPS 2。据认为，OsCPS 1参与GA的生物合成，而OsCPS 2参与植物抗毒素、植物卡桑烷A-E和水稻抗毒素A-F的生物合成。以前已经表明，功能丧失的OsCPS 1突变体显示严重的矮化表型引起的GA缺乏，尽管拥有另一个ent-CDP合酶基因，OsCPS 2。在此，进行实验以解释OsCPS 1和OsCPS 2的非冗余生物学功能。定量逆转录-PCR（qRT-PCR）分析表明，OsCPS 2在水稻幼苗基部（包括第二叶鞘分生组织）的转录水平显著低于OsCPS 1。利用激光显微切割制备的组织样品的qRT-PCR结果表明，OsCPS 1转录本主要定位在维管束组织中，类似于拟南芥CPS，其负责GA的生物合成，而OsCPS 2转录本主要定位在表皮细胞中，以应对环境胁迫，如病原体攻击。此外，OsCPS 1启动子调控下的OsCPS 2转基因补充了OsCPS 1突变体oscps 1 -1的矮化表型。结果表明，两个ent-CDP合酶基因的转录本在水稻中的定位不同，OsCPS 1和OsCPS 2分别负责生长和防御功能。
Expression of the diterpene synthase gene for gibberellin biosynthesis occurs in tissues different from those in which its isoform for phytoalexin biosynthesis is expressed, reflecting their distinct biological roles in rice. Gibberellins (GAs) are diterpenoid phytohormones that regulate various aspects of plant growth. Tetracyclic hydrocarbon ent-kaurene is a biosynthetic intermediate of GAs, and is converted from geranylgeranyl diphosphate, a common precursor of diterpenoids, via ent-copalyl diphosphate (ent-CDP) through successive cyclization reactions catalysed by two distinct diterpene synthases, ent-CDP synthase and ent-kaurene synthase. Rice (Oryza sativa L.) has two ent-CDP synthase genes, OsCPS1 and OsCPS2. It has been thought that OsCPS1 participates in GA biosynthesis, while OsCPS2 participates in the biosynthesis of phytoalexins, phytocassanes A–E, and oryzalexins A–F. It has been shown previously that loss-of-function OsCPS1 mutants display a severe dwarf phenotype caused by GA deficiency despite possessing another ent-CDP synthase gene, OsCPS2. Here, experiments were performed to account for the non-redundant biological function of OsCPS1 and OsCPS2. Quantitative reverse transcription–PCR (qRT–PCR) analysis showed that OsCPS2 transcript levels were drastically lower than those of OsCPS1 in the basal parts, including the meristem of the second-leaf sheaths of rice seedlings. qRT–PCR results using tissue samples prepared by laser microdissection suggested that OsCPS1 transcripts mainly localized in vascular bundle tissues, similar to Arabidopsis CPS, which is responsible for GA biosynthesis, whereas OsCPS2 transcripts mainly localized in epidermal cells that address environmental stressors such as pathogen attack. Furthermore, the OsCPS2 transgene under regulation of the OsCPS1 promoter complemented the dwarf phenotype of an OsCPS1 mutant, oscps1-1. The results indicate that transcripts of the two ent-CDP synthase genes differentially localize in rice plants according to their distinct biological roles, OsCPS1 for growth and OsCPS2 for defence.
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