Dipartimento di Ecologia, Università della Calabria, Arcavacata di Rende, Cosenza, Italy.
Ann Bot. 2011 May;107(7):1223-34. doi: 10.1093/aob/mcq127. Epub 2010 Jul 2.
Aside from those on Arabidopsis, very few studies have focused on spatial expression of cyclin-dependent kinases (CDKs) in root apical meristems (RAMs), and, indeed, none has been undertaken for open meristems. The extent of interfacing between cell cycle genes and plant growth regulators is also an increasingly important issue in plant cell cycle studies. Here spatial expression/localization of an A-type and B-type CDK, auxin and cytokinins are reported in relation to the hitherto unexplored anatomy of RAMs of Cucurbita maxima.
Median longitudinal sections were cut from 1-cm-long primary root tips of C. maxima. Full-length A-type CDKs and a B-type CDK were cloned from C. maxima using degenerate primers, probes of which were localized on sections of RAMs using in situ hybridization. Isopentenyladenine (iPA), trans-zeatin (t-Z) and indole-3yl-acetic acid (IAA) were identified on sections by immunolocalization.
The C. cucurbita RAM conformed to an open transverse (OT) meristem typified by an absence of a clear boundary between the eumeristem and root cap columella, but with a distinctive longitudinally thickened epidermis. Cucma;CDKA;1 expression was detected strongly in the longitudinally thickened epidermis, a tissue with mitotic competence that contributes cells radially to the root cap of OT meristems. Cucma;CDKB2 was expressed mainly in proliferative regions of the RAM and in lateral root primordia. iPA and t-Z were mainly distributed in differentiated cells whilst IAA was distributed more uniformly in all tissues of the RAM.
Cucma;CDKA;1 was expressed most strongly in cells that have proliferative competence whereas Cucma;CDKB2 was confined mainly to mitotic cells. iPA and t-Z marked differentiated cells in the RAM, consistent with the known effect of cytokinins in promoting differentiation in root systems. iPA/t-Z were distributed in a converse pattern to Cucma;CDKB2 expression whereas IAA was detected in most cells in the RAM regardless of their proliferative potential.
除了拟南芥以外，很少有研究关注细胞周期蛋白依赖性激酶（CDKs）在根顶端分生组织（RAM）中的空间表达，实际上，对于开放分生组织，还没有进行过相关研究。细胞周期基因与植物生长调节剂之间的相互作用程度也是植物细胞周期研究中一个日益重要的问题。本文报道了 A 型和 B 型 CDK、生长素和细胞分裂素在尚未探索的南瓜 RAM 解剖结构中的空间表达/定位。
从 1cm 长的南瓜主根根尖切取正中纵向切片。使用简并引物从南瓜中克隆全长 A 型 CDK 和 B 型 CDK，使用原位杂交在 RAM 切片上定位其探针。通过免疫定位在切片上鉴定异戊烯腺嘌呤（iPA）、反式玉米素（t-Z）和吲哚-3-乙酸（IAA）。
南瓜 RAM 符合开放式横向（OT）分生组织的特征，其在表皮细胞和根帽柱状细胞之间没有明确的边界，但具有独特的纵向增厚表皮。Cucma;CDKA;1 在纵向增厚的表皮中表达强烈，这是一种具有有丝分裂能力的组织，它径向贡献细胞到 OT 分生组织的根帽。Cucma;CDKB2 主要在 RAM 的增殖区和侧根原基中表达。iPA 和 t-Z 主要分布在分化细胞中，而 IAA 则在 RAM 的所有组织中分布更为均匀。
Cucma;CDKA;1 在具有增殖能力的细胞中表达最强，而 Cucma;CDKB2 主要局限于有丝分裂细胞。iPA 和 t-Z 标记 RAM 中的分化细胞，这与细胞分裂素在促进根系分化中的已知作用一致。iPA/t-Z 的分布与 Cucma;CDKB2 表达呈相反模式，而 IAA 则在 RAM 中的大多数细胞中被检测到，无论其增殖潜力如何。
