Stokes K D, McAndrew R S, Figueroa R, Vitha S, Osteryoung K W
Department of Botany and Plant Pathology, 166 Plant Biology Building, Michigan State University, East Lansing, Michigan 48824-1312, USA.
Plant Physiol. 2000 Dec;124(4):1668-77. doi: 10.1104/pp.124.4.1668.
In higher plants, two nuclear gene families, FtsZ1 and FtsZ2, encode homologs of the bacterial protein FtsZ, a key component of the prokaryotic cell division machinery. We previously demonstrated that members of both gene families are essential for plastid division, but are functionally distinct. To further explore differences between FtsZ1 and FtsZ2 proteins we investigated the phenotypes of transgenic plants overexpressing AtFtsZ1-1 or AtFtsZ2-1, Arabidopsis members of the FtsZ1 and FtsZ2 families, respectively. Increasing the level of AtFtsZ1-1 protein as little as 3-fold inhibited chloroplast division. Plants with the most severe plastid division defects had 13- to 26-fold increases in AtFtsZ1-1 levels over wild type, and some of these also exhibited a novel chloroplast morphology. Quantitative immunoblotting revealed a correlation between the degree of plastid division inhibition and the extent to which the AtFtsZ1-1 protein level was elevated. In contrast, expression of an AtFtsZ2-1 sense transgene had no obvious effect on plastid division or morphology, though AtFtsZ2-1 protein levels were elevated only slightly over wild-type levels. This may indicate that AtFtsZ2-1 accumulation is more tightly regulated than that of AtFtsZ1-1. Plants expressing the AtFtsZ2-1 transgene did accumulate a form of the protein smaller than those detected in wild-type plants. AtFtsZ2-1 levels were unaffected by increased or decreased accumulation of AtFtsZ1-1 and vice versa, suggesting that the levels of these two plastid division proteins are regulated independently. Taken together, our results provide additional evidence for the functional divergence of the FtsZ1 and FtsZ2 plant gene families.
在高等植物中，两个核基因家族FtsZ1和FtsZ2编码细菌蛋白FtsZ的同源物，FtsZ是原核细胞分裂机制的关键组成部分。我们之前证明这两个基因家族的成员对于质体分裂都是必需的，但功能不同。为了进一步探究FtsZ1和FtsZ2蛋白之间的差异，我们研究了分别过表达FtsZ1和FtsZ2家族的拟南芥成员AtFtsZ1-1或AtFtsZ2-1的转基因植物的表型。将AtFtsZ1-1蛋白水平仅提高3倍就会抑制叶绿体分裂。质体分裂缺陷最严重的植物中，AtFtsZ1-1水平比野生型增加了13至26倍，其中一些还表现出一种新的叶绿体形态。定量免疫印迹显示质体分裂抑制程度与AtFtsZ1-1蛋白水平升高的程度之间存在相关性。相比之下，AtFtsZ2-1正义转基因的表达对质体分裂或形态没有明显影响，尽管AtFtsZ2-1蛋白水平仅比野生型水平略有升高。这可能表明AtFtsZ2-1的积累比AtFtsZ1-1受到更严格的调控。表达AtFtsZ2-1转基因的植物确实积累了一种比在野生型植物中检测到的更小的蛋白形式。AtFtsZ2-1水平不受AtFtsZ1-1积累增加或减少的影响，反之亦然，这表明这两种质体分裂蛋白的水平是独立调控的。综上所述，我们的结果为FtsZ1和FtsZ2植物基因家族的功能差异提供了更多证据。
