傅钰 王苓 龙鸿

摘  要  高等植物生长发育阶段可分为营养生长和生殖生长2个阶段，其中营养生长阶段中只有通过营养生长时相转变方可进入生殖生长阶段。营养生长时相转变（vegetative phase change，VPC）是植物从幼龄期（juvenile stage）到成熟期（adult phase）的转变，受到基因表达的调控。生物钟（circadian clock）相关基因LHY和CCA1单独作用延迟VPC的发生，这2个基因的共同作用下VPC是否受到影响尚未见报道。本研究以拟南芥（Arabidopsis thaliana）为研究对象，通过形态和茎尖分生组织（shoot apical meristem，SAM）解剖结构观察及调控因子miR156和靶基因SPL3的表达变化，分析LHY和CCA1 2个基因在VPC过程中的作用。结果表明：双突变体lhycca1生长周期为15 d，莲座叶第5片时（第10天）出现远轴面表皮毛，此时叶基角和叶长宽比增大且茎尖分生组织凸起明显，miR156和SPL3的表达水平在植物生长发育阶段呈负相关变化。而野生型生长周期为20 d，莲座叶第6片（第15天）时才出现远轴面表皮毛、叶长宽、叶基角、SAM、miR156和SPL3的变化。这些结果说明在LHY和CCA1的共同作用下，VPC提前发生，LHY和CCA1 2个基因参与VPC的调控。

关键词  营养生长时相转变;lhycca1;生物钟;拟南芥

中图分类号  Q945      文献标识码  A

Abstract  Developmental phase of higher plant is composed of two stages： vegetative growth and reproductive growth. Only after the phase transition through vegetative growth does plant go through further reproductive growth. The transition from the juvenile stage to the adult phase in plants is termed vegetative phase change （VPC）， which is regulated by genes. Circadian clock-related genes LHY and CCA1 delay the occurrence of VPC by oneself， but the combined effects of these genes on VPC are not clear. Here， a double mutant lhycca1 of Arabidopsis thaliana was used to investigate the characters of VPC through the observation of plant morphology and anatomical structure of shoot tip meristem （shoot apical meristem， SAM）. The expression of molecular regulatory factor miR156 and its target gene SPL3 in VPC were also analyzed. Our results showed that the growth cycle of the lhycca1 double mutant lasted for 15 d. The onset of abaxial trichomes was on the fifth rosette leaf （the 10th day）. Meanwhile， the base angle and the length： width ratio of leaves increased dramatically， and the shoot tip meristem bulged obviously. During growth and development， the expression levels of miR156 and SPL3 was negatively correlated. By contrast， the growth cycle of the wild-type was about 20 d， with the changes of the abaxial trichomes， length： width ratio of leaves， leaf base angle， SAM， miR156 and SPL3 on the sixth rosette leaf （the 15th day）. These results indicated that VPC in the lhycca1 double mutant occurred in advance under the combined effects of the two genes. LHY and CCA1 genes regulated VPC to some extent.

Keywords  vegetative phase change; lhycca1; circadian clock; Arabidopsis thaliana

DOI  10.3969/j.issn.1000-2561.2019.06.008

高等植物的生命周期經历一系列不同的生长发育阶段，其中会经历营养生长阶段和生殖生长阶段。大多数高等植物的营养生长和生殖生长阶段通常以花芽的分化作为界限，通常一年生植物（拟南芥）在此过渡阶段形态上变化较不明显[1]。其中营养生长阶段又分为幼龄期（juvenile stage）和成熟期（adult phase），从幼龄期到成熟期的转变称为营养生长时相转变（vegetative phase change，VPC）[2]。

一年生拟南芥通常作为研究VPC过程的模式植物，VPC过程会伴随其形态学、细胞学以及分子层面上的变化。……