Black R C, Binns A N, Chang C F, Lynn D G
Biology Department, Pennsylvania State University, Media 19063.
Plant Physiol. 1994 Jul;105(3):989-98. doi: 10.1104/pp.105.3.989.
Mutations at the cytokinin biosynthesis locus (tmr) of Agrobacterium tumefaciens usually result in strains that induce tumors exhibiting the rooty phenotype associated with high auxin-to-cytokinin ratios. However, tobacco (Nicotiana tabacum cv Havana 425) leaf disc explants responded to tmr- mutant strain A356 by producing rapidly growing, unorganized tumors, indicating that these lines can grow in a cytokinin-independent fashion despite the absence of a functional tmr gene. Several methods have been used to characterize the physiological and cellular basis of this phenotype. The results indicate that tmr- tumors have a physiologically distinct mechanism for cytokinin-independent growth in comparison to tumors induced by wild-type bacteria. The cytokinin-independent phenotype of the tmr- transformants appears to be cell autonomous in nature: only the transformed cells and their progeny were capable of cytokinin-independent growth. Specifically, the tmr- tumors did not accumulate cytokinin, and clonal analysis indicated the tmr- transformed cells were not capable of stimulating the growth of neighboring nontransformed cells. Finally, the cytokinin-independent phenotype of the tmr- transformants was shown to be cold sensitive, whereas the wild-type tumors exhibited a cold-resistant cytokinin-independent phenotype. Potential mechanisms for this novel form of cytokinin-independent growth, including the role of the dehydrodiconiferyl alcohol glucosides found in both tumor types, are discussed.
根癌农杆菌细胞分裂素生物合成位点（tmr）的突变通常会导致菌株诱导出表现出与高生长素-细胞分裂素比率相关的根状表型的肿瘤。然而，烟草（烟草品种哈瓦那425）叶片外植体对tmr突变菌株A356的反应是产生快速生长的、无组织的肿瘤，这表明尽管缺乏功能性的tmr基因，但这些品系仍能以不依赖细胞分裂素的方式生长。已经使用了几种方法来表征这种表型的生理和细胞基础。结果表明，与野生型细菌诱导的肿瘤相比，tmr肿瘤具有生理上不同的不依赖细胞分裂素生长的机制。tmr转化体的不依赖细胞分裂素表型在本质上似乎是细胞自主的：只有转化细胞及其后代能够不依赖细胞分裂素生长。具体而言，tmr肿瘤不积累细胞分裂素，克隆分析表明tmr转化细胞不能刺激相邻未转化细胞的生长。最后，tmr转化体的不依赖细胞分裂素表型被证明对冷敏感，而野生型肿瘤表现出抗冷的不依赖细胞分裂素表型。本文讨论了这种新型不依赖细胞分裂素生长形式的潜在机制，包括在两种肿瘤类型中都发现的脱氢松柏醇糖苷的作用。
