Arabidopsis cytokinin-resistant mutant, cnr1, displays altered auxin responses and sugar sensitivity
Arabidopsis cytokinin-resistant mutant, cnr1, displays altered auxin responses and sugar sensitivity
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DOI：
10.1007/s11103-006-9032-z
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发表时间：
2006-10-01
影响因子：
5.1
通讯作者：
Khurana, Jitendra P.
中科院分区：
文献类型：
--
作者：
Laxmi, Ashverya;Paul, Laju K.;Khurana, Jitendra P.
根据年轻的、黑暗生长的幼苗的表型，已经分离到一个细胞分裂素抗性突变体cnr1，它表现出细胞分裂素和生长素诱导的反应改变。突变体幼苗下胚轴较短，顶端钩开放(黑暗条件下)，表现出向生性，子叶发育迟缓，枝条生长减慢，丛生丛生，根短，不定枝增加，根毛减少。这些特征中的许多总是依赖于生长素/细胞分裂素的比率，但cnr1突变体保持了对生长素以及生长素极性运输抑制剂TIBA的正常敏感性，尽管初级生长素反应的AUX/IAA基因上调减少。在下胚轴/根生长抑制试验中，突变体表现出对细胞分裂素的抗性，在组织培养中表现出减少的再生(细胞分裂素反应)，并降低了对细胞分裂素对花青素积累的敏感性。因此可以想象，由于对细胞分裂素的敏感性降低，cnr1。突变体也表现出生长素反应的改变。令人惊讶的是，突变体保持了对细胞分裂素的正常敏感性，以诱导主要反应基因-A型拟南芥反应调节器，尽管它们的基础表达水平与野生型相比显著降低。经高效液相色谱检测，cnr1突变体和野生型的玉米素和玉米素核苷水平以及细胞分裂素氧化酶活性基本一致。Cnr1突变体还表现出对红光敏感(在下胚轴生长抑制实验中)、黑暗中部分光形态建成和对糖敏感的其他特征。Cnr1突变体中的损伤已被定位到1号染色体的顶部，在那里还没有其他已知的细胞分裂素抗性突变体被定位，这表明cnr1突变体定义了一个与激素、光和糖信号有关的新基因座。
Based upon the phenotype of young, dark-grown seedlings, a cytokinin-resistant mutant, cnr1, has been isolated, which displays altered cytokinin- and auxin-induced responses. The mutant seedlings possess short hypocotyls and open apical hooks (in dark), and display agravitropism, hyponastic cotyledons, reduced shoot growth, compact rosettes and short roots with increased adventitious branching and reduced number of root hairs. A number of these features invariably depend upon auxin/cytokinin ratio but the cnr1 mutant retains normal sensitivity towards auxin as well as auxin polar transport inhibitor, TIBA, although upregulation of primary auxin-responsive Aux/IAA genes is reduced. The mutant shows resistance towards cytokinin in hypocotyl/ root growth inhibition assays, displays reduced regeneration in tissue cultures (cytokinin response) and decreased sensitivity to cytokinin for anthocyanin accumulation. It is thus conceivable that due to reduced sensitivity to cytokinin, the cnr1. mutant also shows altered auxin response. Surprisingly, the mutant retains normal sensitivity to cytokinin for induction of primary response genes, the type-A Arabidopsis response regulators, although the basal level of their expression was considerably reduced as compared to the wild-type. The zeatin and zeatin riboside levels, as estimated by HPLC, and the cytokinin oxidase activity were comparable in the cnr1 mutant and the wild-type. The hypersensitivity to red light (in hypocotyl growth inhibition assay), partial photomorphogenesis in dark, and hypersensitivity to sugars, are some other features displayed by the cnr1 mutant. The lesion in the cnr1 mutant has been mapped to the top of chromosome 1 where no other previously known cytokinin-resistant mutant has been mapped, indicating that the cnr1 mutant defines a novel locus involved in hormone, light and sugar signalling.