Coenen C, Lomax T L
Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331-2902, USA.
Plant Physiol. 1998 May;117(1):63-72. doi: 10.1104/pp.117.1.63.
The interactions between the plant hormones auxin and cytokinin throughout plant development are complex, and genetic investigations of the interdependency of auxin and cytokinin signaling have been limited. We have characterized the cytokinin sensitivity of the auxin-resistant diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) in a range of auxin- and cytokinin-regulated responses. Intact, etiolated dgt seedlings showed cross-resistance to cytokinin with respect to root elongation, but cytokinin effects on hypocotyl growth and ethylene synthesis in these seedlings were not impaired by the dgt mutation. Seven-week-old, green wild-type and dgt plants were also equally sensitive to cytokinin with respect to shoot growth and hypocotyl and internode elongation. The effects of cytokinin and the dgt mutation on these processes appeared additive. In tissue culture organ regeneration from dgt hypocotyl explants showed reduced sensitivity to auxin but normal sensitivity to cytokinin, and the effects of cytokinin and the mutation were again additive. However, although callus induction from dgt hypocotyl explants required auxin and cytokinin, dgt calli did not show the typical concentration-dependent stimulation of growth by either auxin or cytokinin observed in wild-type cells. Cross-resistance of the dgt mutant to cytokinin thus was found to be limited to a small subset of auxin- and cytokinin-regulated growth processes affected by the dgt mutation, indicating that auxin and cytokinin regulate plant growth through both shared and separate signaling pathways.
在植物整个发育过程中，植物激素生长素和细胞分裂素之间的相互作用十分复杂，而关于生长素和细胞分裂素信号传导相互依赖性的遗传学研究一直有限。我们已在一系列生长素和细胞分裂素调节的反应中，对番茄（Lycopersicon esculentum Mill.）的生长素抗性双失绿突变体（dgt）的细胞分裂素敏感性进行了表征。完整的黄化dgt幼苗在根伸长方面表现出对细胞分裂素的交叉抗性，但细胞分裂素对这些幼苗下胚轴生长和乙烯合成的影响并未因dgt突变而受损。7周龄的绿色野生型和dgt植株在茎生长、下胚轴和节间伸长方面对细胞分裂素也同样敏感。细胞分裂素和dgt突变对这些过程的影响似乎是相加的。在组织培养中，dgt下胚轴外植体的器官再生对生长素的敏感性降低，但对细胞分裂素的敏感性正常，细胞分裂素和该突变的影响同样是相加的。然而，尽管从dgt下胚轴外植体诱导愈伤组织需要生长素和细胞分裂素，但dgt愈伤组织并未表现出野生型细胞中观察到的生长素或细胞分裂素对生长的典型浓度依赖性刺激。因此，发现dgt突变体对细胞分裂素的交叉抗性仅限于受dgt突变影响的生长素和细胞分裂素调节的生长过程的一小部分，这表明生长素和细胞分裂素通过共享和独立的信号通路调节植物生长。
