Deikman J, Ulrich M
Department of Biology, University Park 16802.
Planta. 1995;195(3):440-9. doi: 10.1007/BF00202603.
Cytokinins influence several fundamental processes of plant growth and development, including cell division and organogenesis. To identify genes involved in cytokinin response, a screen was carried out for mutants of Arabidopsis thaliana (L.) Heynh. that are resistant to elevated levels of exogenous cytokinins. One such mutant was isolated and named cyr1. A cross to another Arabidopsis cytokinin-resistant mutant, ckr1 (Su and Howell 1992), indicated that the two mutants are not allelic. The recessive cyr1 mutation causes tenfold decreased sensitivity to benzyladenine in a root-elongation assay but does not confer resistance of roots to indole-3-acetic acid, the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, or abscisic acid. The mutant has increased sensitivity to abscisic acid. This mutation is apparently pleiotropic, giving rise to shoot abnormalities. The phenotype of the cyr1 shoot includes abbreviated development with reduction in cotyledon and leaf expansion, limited leaf production, reduced chlorophyll accumulation, failure to accumulate anthocyanins in response to cytokinins, and the formation of a single infertile flower. These traits, as well as root resistance to cytokinin, are all consistent with a defect in cytokinin action, and are probably due to mutation of a single gene. The cyr1 gene is located on chromosome 5, between 76.2 and 77.6 cM.
细胞分裂素影响植物生长和发育的几个基本过程，包括细胞分裂和器官发生。为了鉴定参与细胞分裂素应答的基因，对拟南芥（L.）Heynh.的突变体进行了筛选，这些突变体对外源细胞分裂素水平升高具有抗性。分离出了一个这样的突变体并命名为cyr1。与另一个拟南芥细胞分裂素抗性突变体ckr1杂交（Su和Howell，1992），表明这两个突变体不是等位基因。隐性cyr1突变在根伸长试验中导致对苄基腺嘌呤的敏感性降低10倍，但并未使根对吲哚-3-乙酸、乙烯前体1-氨基环丙烷-1-羧酸或脱落酸产生抗性。该突变体对脱落酸的敏感性增加。此突变显然是多效性的，导致地上部分出现异常。cyr1地上部分的表型包括发育缩短，子叶和叶片扩展减少，叶片产生受限，叶绿素积累减少，对细胞分裂素不积累花青素，以及形成一朵不育的单花。这些性状，以及根对细胞分裂素的抗性，都与细胞分裂素作用缺陷一致，并且可能是由于单个基因的突变所致。cyr1基因位于第5号染色体上，在76.2和77.6厘摩之间。
