Falcone Andrea, Nelissen Hilde, Fleury Delphine, Van Lijsebettens Mieke, Bitonti Maria Beatrice
Università della Calabria, Dipartimento di Ecologia, Via ponte P. Bucci, Cubo 6B, I-87036, Arcavacata di Rende, CS, Italia.
Ann Bot. 2007 Aug;100(2):261-70. doi: 10.1093/aob/mcm102. Epub 2007 Jun 11.
Leaf growth is a complex developmental process controlled by genetic and environmental factors and is determined by a proliferation, expansion and maturation phase. Mutational analysis in Arabidopsis thaliana showed that leaf size and shape is dependent on cell division and cell expansion activity. An investigation was made at the cytophysiological and ultrastructural level of the elo1 mutant of Arabidopsis thaliana, which is defective in one of the components of the histone acetyl transferase Elongator complex and displays a distinct 'narrow leaves' phenotype, owing to a reduced cell number and no transition between petiole and lamina. Relative expression levels of three sucrose metabolism/transport-related genes were also investigated. The aim was to determine the physiological basis of leaf morphology in this mutant, by investigating the modulatory role of sucrose.
The elo1 mutant was taken as representative of all the elo mutations and investigated at cytophysiological level. A germination test and growth assays were performed on seedlings grown for 21 d at different sucrose concentrations. Leaf morphometric and ultrastructural features were also investigated by image analysis and electron microscopy, respectively. Finally, a quantitative PCR (qPCR) analysis was performed with three sucrose metabolism/transport-related genes that were investigated under different sucrose concentrations.
elo1 plants at high sucrose concentrations exhibited an enhancement of germination and inhibition of leaf growth as compared with wild-type plants. qPCR experiments with three sucrose metabolism/transport-related genes showed an interaction between sucrose availability and the elo1 mutation. Furthermore, electron microscopy analysis provided the first ultrastructural description of an elo mutant, which showed a hypotonic vacuole, alterations in the size of grana and starch grains in the chloroplasts, and the massive presence of Golgi vesicles in the cytoplasm.
Based on the results obtained it is proposed that mechanisms producing carbon assimilates or importing sucrose could be affected in elo1 plants and could account for the observed differences, implying a role for Elongator in the regulation of these processes.
叶片生长是一个受遗传和环境因素控制的复杂发育过程，由细胞增殖、扩展和成熟阶段决定。拟南芥的突变分析表明，叶片大小和形状取决于细胞分裂和细胞扩展活动。本研究在细胞生理和超微结构水平上对拟南芥elo1突变体进行了调查，该突变体在组蛋白乙酰转移酶延伸因子复合物的一个组分中存在缺陷，由于细胞数量减少且叶柄与叶片之间无过渡，表现出明显的“窄叶”表型。还研究了三个蔗糖代谢/转运相关基因的相对表达水平。目的是通过研究蔗糖的调节作用来确定该突变体叶片形态的生理基础。
以elo1突变体作为所有elo突变的代表，在细胞生理水平上进行研究。对在不同蔗糖浓度下生长21天的幼苗进行发芽试验和生长测定。还分别通过图像分析和电子显微镜研究了叶片形态测量和超微结构特征。最后，对在不同蔗糖浓度下研究的三个蔗糖代谢/转运相关基因进行了定量PCR（qPCR）分析。
与野生型植物相比，高蔗糖浓度下的elo1植物发芽增强，叶片生长受到抑制。对三个蔗糖代谢/转运相关基因进行的qPCR实验表明，蔗糖供应与elo1突变之间存在相互作用。此外，电子显微镜分析首次提供了elo突变体的超微结构描述，显示出低渗液泡、叶绿体中基粒和淀粉粒大小的改变以及细胞质中大量存在的高尔基体囊泡。
根据所得结果推测，elo1植物中产生碳同化产物或导入蔗糖的机制可能受到影响，这可能解释了观察到的差异，意味着延伸因子在这些过程的调节中起作用。
