Sheahan Michael B, Collings David A, Rose Ray J, McCurdy And David W
School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia.
Plants (Basel). 2020 Feb 10;9(2):225. doi: 10.3390/plants9020225.
In Arabidopsis, the actin gene family comprises eight expressed and two non-expressed () genes. Of the eight expressed isoforms, , and are differentially expressed in vegetative tissues and may perform specific roles in development. Using tobacco mesophyll protoplasts, we previously demonstrated that actin-dependent clustering of chloroplasts around the nucleus prior to cell division ensures unbiased chloroplast inheritance. Here, we report that actin-dependent chloroplast clustering in Arabidopsis mesophyll protoplasts is defective in mutants, but not or . expression was upregulated during protoplast culture whereas and expression did not substantially change. In , expression increased in response to loss of , whereas in , neither nor expression changed appreciably in response to the absence of ACT7. Semi-quantitative immunoblotting revealed increased actin concentrations during culture, although total actin in was only two-thirds that of wild-type or after 96 h culture Over-expression of and under control of regulatory sequences restored normal levels of chloroplast clustering. These results are consistent with a requirement for ACT7 in actin-dependent chloroplast clustering due to reduced levels of actin protein and gene induction in mutants, rather than strong functional specialization of the ACT7 isoform.
在拟南芥中，肌动蛋白基因家族包含8个表达基因和2个不表达（）基因。在8个表达的异构体中，、和在营养组织中差异表达，可能在发育中发挥特定作用。我们之前利用烟草叶肉原生质体证明，细胞分裂前叶绿体围绕细胞核的肌动蛋白依赖性聚集确保了叶绿体的无偏遗传。在此，我们报道拟南芥叶肉原生质体中肌动蛋白依赖性叶绿体聚集在突变体中存在缺陷，但在或突变体中无缺陷。在原生质体培养过程中表达上调，而和的表达没有显著变化。在中，表达因缺失而增加，而在中，缺失ACT7后和的表达均无明显变化。半定量免疫印迹显示培养过程中肌动蛋白浓度增加，尽管培养96小时后中的总肌动蛋白仅为野生型或的三分之二。在调控序列控制下过表达和可恢复叶绿体聚集的正常水平。这些结果表明，由于突变体中肌动蛋白蛋白水平降低和基因诱导，肌动蛋白依赖性叶绿体聚集需要ACT7，而不是ACT7异构体的强大功能特化。
