LATERAL BRANCHING OXIDOREDUCTASE acts in the final stages of strigolactone biosynthesis in Arabidopsis
LATERAL BRANCHING OXIDOREDUCTASE acts in the final stages of strigolactone biosynthesis in Arabidopsis
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DOI：
10.1073/pnas.1601729113
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发表时间：
2016-05-31
影响因子：
11.1
通讯作者：
Beveridge, Christine A.
中科院分区：
文献类型：
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作者：
Brewer, Philip B.;Yoneyama, Kaori;Beveridge, Christine A.
独角己内酯是一类化学结构多样但又相互关联的植物化合物。它们在广泛的植物物种中具有相似的生物活性，可以优化植物的生长发育，促进土壤微生物的相互作用。卡拉内酯是独角甾内酯的常见前体，由许多不同物种中发现的保守酶产生。来自水稻和拟南芥的MORE AXILLARY GROWTH1 （MAX1）细胞色素P450的版本从卡拉内酯中产生特定的独角甘内酯亚群。然而，天然独角酯内酯的多样性表明，还有其他酶参与其中，但仍有待发现。在这里，我们使用了一种创新的方法，揭示了一种缺失的酶参与独角麦内酯代谢。通过使用转录组学方法，包括一系列修饰独角麦内酯生物合成基因表达的处理，加上反向遗传学，我们鉴定了LATERAL BRANCHING OXIDOREDUCTASE (LBO)，这是一个编码2-氧戊二酸和铁（II）依赖性双加氧酶超家族的氧化还原酶样酶的基因。拟南芥lbo突变体表现出茎分枝增加，但lbo突变体没有增强最大突变体表型。接枝表明，LBO是可接枝传输信号所必需的，而接枝传输信号又需要MAX1的乘积。突变体lbo背景显示对MAX1底物卡拉内酯和MAX1下游产物卡拉内酯甲酯（MeCLA）的反应降低。此外，lbo突变体含有更多的这些化合物，并且lbo蛋白特异性地将MeCLA转化为一种未识别的孤孤内酯样化合物。因此，在拟南芥和其他种子植物中，LBO功能可能在独角麦内酯生物合成的后期步骤中发挥重要作用，以抑制芽分枝。
Strigolactones are a group of plant compounds of diverse but related chemical structures. They have similar bioactivity across a broad range of plant species, act to optimize plant growth and development, and promote soil microbe interactions. Carlactone, a common precursor to strigolactones, is produced by conserved enzymes found in a number of diverse species. Versions of the MORE AXILLARY GROWTH1 (MAX1) cytochrome P450 from rice and Arabidopsis thaliana make specific subsets of strigolactones from carlactone. However, the diversity of natural strigolactones suggests that additional enzymes are involved and remain to be discovered. Here, we use an innovative method that has revealed a missing enzyme involved in strigolactone metabolism. By using a transcriptomics approach involving a range of treatments that modify strigolactone biosynthesis gene expression coupled with reverse genetics, we identified LATERAL BRANCHING OXIDOREDUCTASE (LBO), a gene encoding an oxidoreductase-like enzyme of the 2-oxoglutarate and Fe(II)-dependent dioxygenase superfamily. Arabidopsis lbo mutants exhibited increased shoot branching, but the lbo mutation did not enhance the max mutant phenotype. Grafting indicated that LBO is required for a graft-transmissible signal that, in turn, requires a product of MAX1. Mutant lbo backgrounds showed reduced responses to carlactone, the substrate of MAX1, and methyl carlactonoate (MeCLA), a product downstream of MAX1. Furthermore, lbo mutants contained increased amounts of these compounds, and the LBO protein specifically converts MeCLA to an unidentified strigolactone-like compound. Thus, LBO function may be important in the later steps of strigolactone biosynthesis to inhibit shoot branching in Arabidopsis and other seed plants.