Department of Biology, University of Antwerp, Antwerpen, Belgium.
PLoS One. 2013 Nov 27;8(11):e82596. doi: 10.1371/journal.pone.0082596. eCollection 2013.
The root of Arabidopsis thaliana is used as a model system to unravel the molecular nature of cell elongation and its arrest. From a micro-array performed on roots that were treated with aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, a Small auxin-up RNA (SAUR)-like gene was found to be up regulated. As it appeared as the 76th gene in the family, it was named SAUR76. Root and leaf growth of overexpression lines ectopically expressing SAUR76 indicated the possible involvement of the gene in the division process. Using promoter::GUS and GFP lines strong expression was seen in endodermal and pericycle cells at the end of the elongation zone and during several stages of lateral root primordia development. ACC and IAA/NAA were able to induce a strong up regulation of the gene and changed the expression towards cortical and even epidermal cells at the beginning of the elongation zone. Confirmation of this up regulation of expression was delivered using qPCR, which also indicated that the expression quickly returned to normal levels when the inducing IAA-stimulus was removed, a behaviour also seen in other SAUR genes. Furthermore, confocal analysis of protein-GFP fusions localized the protein in the nucleus, cytoplasm and plasma membrane. SAUR76 expression was quantified in several mutants in ethylene and auxin-related pathways, which led to the conclusion that the expression of SAUR76 is mainly regulated by the increase in auxin that results from the addition of ACC, rather than by ACC itself.
拟南芥的根被用作模型系统，以揭示细胞伸长及其阻滞的分子本质。从用乙烯前体氨基环丙烷-1-羧酸（ACC）处理的根进行的微阵列中，发现了一个小生长素 RNA（SAUR）样基因被上调。由于它出现在家族的第 76 个基因中，因此被命名为 SAUR76。异位表达 SAUR76 的过表达系的根和叶片生长表明该基因可能参与分裂过程。使用启动子::GUS 和 GFP 系，在伸长区末端和侧根原基发育的几个阶段，可以在内皮层和周皮细胞中观察到强烈的表达。ACC 和 IAA/NAA 能够强烈诱导该基因的上调，并将表达改变为伸长区开始时的皮层甚至表皮细胞。使用 qPCR 证实了这种表达的上调，这也表明当去除诱导的 IAA 刺激时，表达很快恢复到正常水平，这种行为也在其他 SAUR 基因中观察到。此外，使用 GFP 融合蛋白的共聚焦分析将该蛋白定位于细胞核、细胞质和质膜中。在与乙烯和生长素相关途径相关的几种突变体中对 SAUR76 的表达进行了定量，得出的结论是 SAUR76 的表达主要受由 ACC 添加引起的生长素增加的调节，而不是由 ACC 本身调节。
