Western T L, Burn J, Tan W L, Skinner D J, Martin-McCaffrey L, Moffatt B A, Haughn G W
Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4.
Plant Physiol. 2001 Nov;127(3):998-1011.
In Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type producing extracellular pectinaceous mucilage and a volcano-shaped secondary cell wall. Differentiation involves a regulated series of cytological events including growth, cytoplasmic rearrangement, mucilage synthesis, and secondary cell wall production. We have tested the potential of Arabidopsis seed coat epidermal cells as a model system for the genetic analysis of these processes. A screen for mutants defective in seed mucilage identified five novel genes (MUCILAGE-MODIFIED [MUM]1-5). The seed coat development of these mutants, and that of three previously identified ones (TRANSPARENT TESTA GLABRA1, GLABRA2, and APETALA2) were characterized. Our results show that the genes identified define several events in seed coat differentiation. Although APETALA2 is needed for differentiation of both outer layers of the seed coat, TRANSPARENT TESTA GLABRA1, GLABRA2, and MUM4 are required for complete mucilage synthesis and cytoplasmic rearrangement. MUM3 and MUM5 may be involved in the regulation of mucilage composition, whereas MUM1 and MUM2 appear to play novel roles in post-synthesis cell wall modifications necessary for mucilage extrusion.
在拟南芥中，受精作用诱导外珠被的表皮细胞分化为一种特殊的种皮细胞类型，该细胞类型可产生细胞外果胶黏液和火山形状的次生细胞壁。分化过程涉及一系列受调控的细胞学事件，包括生长、细胞质重排、黏液合成和次生细胞壁形成。我们已测试拟南芥种皮表皮细胞作为这些过程遗传分析模型系统的潜力。对种子黏液缺陷型突变体的筛选鉴定出五个新基因（黏液修饰[MUM]1 - 5）。对这些突变体以及之前鉴定出的三个突变体（透明种皮GLABRA1、GLABRA2和APETALA2）的种皮发育进行了表征。我们的结果表明，所鉴定的基因定义了种皮分化中的几个事件。虽然APETALA2是种皮两层分化所必需的，但透明种皮GLABRA1、GLABRA2和MUM4是完全黏液合成和细胞质重排所必需的。MUM3和MUM5可能参与黏液成分的调控，而MUM1和MUM2似乎在黏液挤出所需的合成后细胞壁修饰中发挥新作用。
