Nooden L D
Department of Botany, University of Michigan, Ann Arbor, Michigan 48104.
Plant Physiol. 1968 Feb;43(2):140-50. doi: 10.1104/pp.43.2.140.
Selective inhibitors were used to study the connection between nucleic acid synthesis and indoleacetic acid (IAA) induction of cell enlargement. Actinomycin D (act D) and azaguanine (azaG) almost completely inhibit IAA-induced growth in aged artichoke tuber disks when they are added simultaneously with IAA. In contrast, when they are added 24 hours after the hormone, these inhibitors have little or no effect on the induced growth which continues for 48 hours or more with little or no inhibition. Inhibitors of protein synthesis still stop growth when applied 24 hours after the IAA, thus protein synthesis and presumably supporting metabolism are still essential.In corn coleoptile sections auxin-induced growth did not show any pronounced tendency to become less sensitive to act D as the IAA treatment progressed. Act D did not completely inhibit the response to IAA unless the sections were pretreated with act D for 6 hours. In contrast to act D, cordycepin produced almost complete inhibition of IAA-induced growth when added with the IAA.Although IAA has a very large and very rapid stimulatory effect (within 10 min) on incorporation of (32)P-orthophosphate into RNA in disks, it did not cause a detectable change in the base composition of the RNA synthesized. Furthermore, the promotive effect could be accounted for through increased uptake of the (32)P. That much of the RNA synthesis in these tissues is not necessary for auxin action is indicated by the results with fluorouracil (FU). FU strongly inhibits RNA synthesis, probably acting preferentially on ribosomal RNA synthesis, without inhibiting auxin-induced growth in the disks or coleoptile sections. FU also strongly inhibited respiration in auxin-treated disks indicating that the large promotion of respiration by auxin likewise may not be entirely necessary for growth.At least in the artichoke disks, RNA synthesis is required for auxin induction of cell enlargement and not for cell enlargement itself.The possible relationships of auxin induction of cell enlargement and RNA synthesis are discussed.
使用选择性抑制剂来研究核酸合成与吲哚乙酸（IAA）诱导细胞膨大之间的联系。放线菌素D（Act D）和氮杂鸟嘌呤（azaG）在与IAA同时添加时，几乎能完全抑制老龄洋蓟块茎切片中IAA诱导的生长。相反，当在激素处理24小时后添加这些抑制剂时，它们对诱导生长几乎没有影响，诱导生长会持续48小时或更长时间，几乎没有受到抑制。蛋白质合成抑制剂在IAA处理24小时后应用时仍会阻止生长，因此蛋白质合成以及可能的支持性代谢仍然至关重要。在玉米胚芽鞘切段中，随着IAA处理的进行，生长素诱导的生长对Act D并未表现出任何明显的敏感性降低趋势。除非切段用Act D预处理6小时，否则Act D不会完全抑制对IAA的反应。与Act D相反，蛹虫草菌素与IAA一起添加时几乎能完全抑制IAA诱导的生长。尽管IAA对圆盘切片中（32）P - 正磷酸盐掺入RNA具有非常大且非常迅速的刺激作用（在10分钟内），但它并未导致合成的RNA碱基组成发生可检测到的变化。此外，促进作用可以通过增加（）P的摄取来解释。氟尿嘧啶（FU）的结果表明，这些组织中的许多RNA合成对于生长素作用并非必需。FU强烈抑制RNA合成，可能优先作用于核糖体RNA合成，而不抑制圆盘切片或胚芽鞘切段中生长素诱导的生长。FU还强烈抑制生长素处理的圆盘切片中的呼吸作用，这表明生长素对呼吸作用的大幅促进同样可能并非生长所完全必需。至少在洋蓟圆盘切片中，RNA合成是生长素诱导细胞膨大所必需的，而不是细胞膨大本身所必需的。讨论了生长素诱导细胞膨大与RNA合成之间可能的关系。
