Primary root protophloem differentiation requires balanced phosphatidylinositol-4,5-biphosphate levels and systemically affects root branching
Primary root protophloem differentiation requires balanced phosphatidylinositol-4,5-biphosphate levels and systemically affects root branching
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DOI：
10.1242/dev.118364
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发表时间：
2015-04-15
期刊：
影响因子：
4.6
通讯作者：
Hardtke, Christian S.
中科院分区：
文献类型：
--
作者：
Rodriguez-Villalon, Antia;Gujas, Bojan;Hardtke, Christian S.
原生韧皮部是生长中的植物器官（如根分生组织）中的特化维管组织。在拟南芥突变体与受损的主根原韧皮部分化，短根（brx）和章鱼（ops），分生组织的活动，从而整体根生长强烈减少。原韧皮部特异性假定磷酸肌醇5-磷酸酶子叶血管模式2（CVP 2）中的第二个位点突变，而不是其同源物CVP 2-LIKE 1（CVL 1）中的第二个位点突变，部分挽救了brx缺陷。与这一发现一致，野生型背景中的CVP 2活性亢进重建了brx表型。然而，奇怪的是，虽然cvp 2或cvl 1单突变体没有表现出明显的根缺陷，但cvp 2 cvl 1双突变体的根表型与brx或ops相似，尽管如预期的那样，cvp 2 cvl 1幼苗含有更多的磷脂酰肌醇-4，5-二磷酸。因此，紧密平衡的磷脂酰肌醇-4，5-二磷酸水平似乎对适当的原生韧皮部分化至关重要。在遗传学上，OPS作用于磷脂酰肌醇-4，5-二磷酸水平的下游，因为cvp 2突变不能挽救ops缺陷，而增加的OPS剂量挽救cvp 2 cvl 1缺陷。最后，所有三个突变体显示更高的密度和侧根的出现加速，这与根分化区生长素反应增加相关。这种表型也是通过应用抑制原韧皮部分化的肽CLAVATA 3/胚胎周围区26（CLE 26）和CLE 45产生的。因此，主根原生韧皮部的局部变化系统地塑造了整个根系结构。
Protophloem is a specialized vascular tissue in growing plant organs, such as root meristems. In Arabidopsis mutants with impaired primary root protophloem differentiation, brevis radix (brx) and octopus (ops), meristematic activity and consequently overall root growth are strongly reduced. Second site mutation in the protophloem-specific presumed phosphoinositide 5-phosphataseCOTYLEDON VASCULAR PATTERN 2 (CVP2), but not in its homolog CVP2-LIKE 1 (CVL1), partially rescues brx defects. Consistent with this finding, CVP2 hyperactivity in a wild-type background recreates a brx phenotype. Paradoxically, however, while cvp2 or cvl1 single mutants display no apparent root defects, the root phenotype of cvp2 cvl1 double mutants is similar to brx or ops, although, as expected, cvp2 cvl1 seedlings contain more phosphatidylinositol-4,5-biphosphate. Thus, tightly balanced phosphatidylinositol-4,5-biphosphate levels appear essential for proper protophloem differentiation. Genetically, OPS acts downstream of phosphatidylinositol-4,5-biphosphate levels, as cvp2 mutation cannot rescue ops defects, whereas increased OPS dose rescues cvp2 cvl1 defects. Finally, all three mutants display higher density and accelerated emergence of lateral roots, which correlates with increased auxin response in the root differentiation zone. This phenotype is also created by application of peptides that suppress protophloem differentiation, CLAVATA3/EMBRYO SURROUNDING REGION 26 (CLE26) and CLE45. Thus, local changes in the primary root protophloem systemically shape overall root system architecture.