Chloroplast movement is regulated by dynamic reorganization of the actin cytoskeleton. To gain insight into the function of ACT2 in chloroplast movement, we examined the effect of the act2-3 mutation, in which a T-DNA is inserted at the second exon of the ACT2 gene, and investigated a transgenic Arabidopsis plant expressing the GFP-ACT2 fusion protein. Chloroplast movement in the act2-3 mutant was retarded, especially during the avoidance response, compared with that in the WT. We further verified the physiological response of transgenic Arabidopsis expressing the GFP-ACT2 fusion gene with a 6xGSS linker sequence, which was recently reported to enable the direct visualization of actin filaments in a transient expression system. Although the expression of GFP-ACT2 had highly detrimental effects on the growth and development of transgenic Arabidopsis plants, GFP-ACT2 was incorporated into chloroplast actin (cp-actin) filaments instead of cortical actin filaments. The analyses of the act2 mutant and GFP-ACT2 transgenic plants suggest that ACT2 functions in chloroplast movement as a component of cp-actin filaments and that cp-actin filaments are differently regulated compared to cortical actin filaments.

叶绿体的运动是由肌动蛋白细胞骨架的动态重组来调节的。为了深入了解ACT2在叶绿体运动中的功能，我们检查了act2-3突变的作用，其中在ACT2基因的第二个外显子处插入了T-DNA ，并研究了表达GFP-的转基因拟南芥植物ACT2融合蛋白。与野生型相比，act2-3突变体的叶绿体运动受阻，特别是在回避反应过程中。我们进一步验证了表达GFP-ACT2的转基因拟南芥的生理反应。具有6xGSS接头序列的融合基因，据报道，该基因可在瞬时表达系统中直接显示肌动蛋白丝。尽管GFP-ACT2的表达对转基因拟南芥植物的生长和发育具有很大的不利影响，但GFP-ACT2并入叶绿体肌动蛋白（cp-actin）细丝而不是皮质肌动蛋白细丝。对act2突变体和GFP-ACT2转基因植物的分析表明，ACT2在叶绿体运动中作为cp-actin细丝的成分起作用，并且与皮质肌动蛋白细丝相比，cp-actin细丝受到不同的调节。