Harrar Yaël, Bellec Yannick, Bellini Catherine, Faure Jean-Denis
Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, 78026 Versailles cedex, France.
Plant Physiol. 2003 Jul;132(3):1217-27. doi: 10.1104/pp.102.019026.
PASTICCINO (PAS) genes are required for coordinated cell division and differentiation during plant development. In loss-of-function pas mutants, plant aerial tissues showed ectopic cell division that was specifically enhanced by cytokinins, leading to disorganized tumor-like tissue. To determine the role of the PAS genes in controlling cell proliferation, we first analyzed the expression profiles of several genes involved in cell division and meristem function. Differentiated and meristematic cells of the pas mutants were more competent for cell division as illustrated by the ectopic and enlarged expression profiles of CYCLIN-DEPENDENT KINASE A and CYCLIN B1. The expression of meristematic homeobox genes KNOTTED-LIKE IN ARABIDOPSIS (KNAT2, KNAT6), and SHOOT MERISTEMLESS was also increased in pas mutants. Moreover, the loss of meristem function caused by shoot meristemless mutation can be suppressed by pas2. The KNAT2 expression pattern defines an enlarged meristematic zone in pas mutants that can be mimicked in wild type by cytokinin treatment. Cytokinin induction of the primary cytokinin response markers, ARABIDOPSIS RESPONSE REGULATOR (ARR5 and ARR6), was enhanced and lasted longer in pas mutants, suggesting that PAS genes in wild type repress cytokinin responses. The expression of the cytokinin-regulated cyclin D, cyclin D3.1, was nonetheless not modified in pas mutants. However, primary auxin response genes were down-regulated in pas mutants, as shown by a lower auxin induction of IAA4 and IAA1 genes, demonstrating that the auxin response was also modified. Altogether, our results suggest that PAS genes are involved in the hormonal control of cell division and differentiation.
PASTICCINO（PAS）基因在植物发育过程中对细胞分裂和分化的协调至关重要。在功能缺失的pas突变体中，植物地上组织表现出异位细胞分裂，这种分裂被细胞分裂素特异性增强，导致组织紊乱，形成肿瘤样组织。为了确定PAS基因在控制细胞增殖中的作用，我们首先分析了几个参与细胞分裂和分生组织功能的基因的表达谱。pas突变体的分化细胞和分生细胞对细胞分裂更具能力，这通过细胞周期蛋白依赖性激酶A和细胞周期蛋白B1的异位和扩大表达谱得以体现。拟南芥中分生组织同源异型盒基因KNOTTED-LIKE（KNAT2、KNAT6）和SHOOT MERISTEMLESS在pas突变体中的表达也增加了。此外，shoot meristemless突变导致的分生组织功能丧失可被pas2抑制。KNAT2的表达模式在pas突变体中定义了一个扩大的分生组织区域，细胞分裂素处理可在野生型中模拟这种模式。在pas突变体中，细胞分裂素对主要细胞分裂素反应标记物拟南芥反应调节因子（ARR5和ARR6）的诱导增强且持续时间更长，这表明野生型中的PAS基因抑制细胞分裂素反应。然而，细胞分裂素调节的细胞周期蛋白D即细胞周期蛋白D3.1在pas突变体中的表达未发生改变。但是，主要生长素反应基因在pas突变体中下调，如IAA4和IAA1基因的生长素诱导较低所示，这表明生长素反应也发生了改变。总之，我们的结果表明PAS基因参与了细胞分裂和分化的激素调控。
