Konishi Mineko, Sugiyama Munetaka
Botanical Gardens, Graduate School of Science, The University of Tokyo, Hakusan 3-7-1, Bunkyo-ku, Tokyo 112-0001, Japan.
Development. 2003 Dec;130(23):5637-47. doi: 10.1242/dev.00794. Epub 2003 Oct 1.
When cultured on media containing the plant growth regulator auxin, hypocotyl explants of Arabidopsis thaliana generate adventitious roots. As a first step to investigate the genetic basis of adventitious organogenesis in plants, we isolated nine temperature-sensitive mutants defective in various stages in the formation of adventitious roots: five root initiation defective (rid1 to rid5) mutants failed to initiate the formation of root primordia; in one root primordium defective (rpd1) mutant, the development of root primordia was arrested; three root growth defective (rgd1, rgd2, and rgd3) mutants were defective in root growth after the establishment of the root apical meristem. The temperature sensitivity of callus formation and lateral root formation revealed further distinctions between the isolated mutants. The rid1 mutant was specifically defective in the reinitiation of cell proliferation from hypocotyl explants, while the rid2 mutant was also defective in the reinitiation of cell proliferation from root explants. These two mutants also exhibited abnormalities in the formation of the root apical meristem when lateral roots were induced at the restrictive temperature. The rgd1 and rgd2 mutants were deficient in root and callus growth, whereas the rgd3 mutation specifically affected root growth. The rid5 mutant required higher auxin concentrations for rooting at the restrictive temperature, implying a deficiency in auxin signaling. The rid5 phenotype was found to result from a mutation in the MOR1/GEM1 gene encoding a microtubule-associated protein. These findings about the rid5 mutant suggest a possible function of the microtubule system in auxin response.
在含有植物生长调节剂生长素的培养基上培养时，拟南芥的下胚轴外植体可产生不定根。作为研究植物不定器官发生遗传基础的第一步，我们分离出了9个在不定根形成的各个阶段存在缺陷的温度敏感突变体：5个根起始缺陷（rid1至rid5）突变体未能起始根原基的形成；在1个根原基缺陷（rpd1）突变体中，根原基的发育停滞；3个根生长缺陷（rgd1、rgd2和rgd3）突变体在根顶端分生组织建立后根生长存在缺陷。愈伤组织形成和侧根形成的温度敏感性揭示了分离出的突变体之间的进一步差异。rid1突变体在下胚轴外植体细胞增殖的重新起始方面存在特异性缺陷，而rid2突变体在根外植体细胞增殖的重新起始方面也存在缺陷。当在限制温度下诱导侧根时，这两个突变体在根顶端分生组织的形成上也表现出异常。rgd1和rgd2突变体在根和愈伤组织生长方面存在缺陷，而rgd3突变则特异性地影响根生长。rid5突变体在限制温度下生根需要更高浓度 的生长素，这意味着生长素信号传导存在缺陷。发现rid5表型是由编码微管相关蛋白的MOR1/GEM1基因突变引起的。关于rid5突变体的这些发现表明微管系统在生长素应答中可能具有作用。
