Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
Division of Crop Development, Central Region Agricultural Research Center, National Agriculture and Food Research Organization (NARO), Niigata, Japan.
PLoS One. 2019 May 23;14(5):e0217212. doi: 10.1371/journal.pone.0217212. eCollection 2019.
The endosperm cell wall affects post-harvest grain quality by affecting the mechanical fragility and water absorption of the grain. Therefore, understanding the mechanism underlying endosperm cell wall synthesis is important for determining the growth and quality of cereals. However, the molecular machinery mediating endosperm cell wall biosynthesis is not well understood. In this study, we investigated the role of Oryza sativa Brittle Culm 1-like 6 (OsBC1L6), a member of the COBRA-like protein family, in cellulose synthesis in rice. OsBC1L6 mRNA was expressed in ripening seeds during endosperm enlargement. When OsBC1L6-RFP was expressed in Arabidopsis cell cultures, this fusion protein was transported to the plasma membrane. To investigate the target molecules of OsBC1L6, we analyzed the binding interactions of OsBC1L6 with cellohexaose and the analogs using surface plasmon resonance, determining that cellohexaose bound to OsBC1L6. The β-glucan contents were significantly reduced in OsBC1L6-RNAi calli and OsBC1L6-deficient seeds from a Tos insertion mutant, compared to their wild-type counterparts. These findings suggest that OsBC1L6 modulates β-glucan synthesis during endosperm cell wall formation by interacting with cellulose moieties on the plasma membrane during seed ripening.
胚乳细胞壁通过影响谷物的机械脆性和吸水性来影响收获后的谷物品质。因此，了解胚乳细胞壁合成的机制对于确定谷物的生长和品质是很重要的。然而，介导胚乳细胞壁生物合成的分子机制尚不清楚。在这项研究中，我们研究了水稻中 COBRA 样蛋白家族成员 Oryza sativa Brittle Culm 1-like 6（OsBC1L6）在纤维素合成中的作用。OsBC1L6mRNA 在胚乳增大过程中在成熟种子中表达。当 OsBC1L6-RFP 在拟南芥细胞培养物中表达时，这种融合蛋白被运送到质膜。为了研究 OsBC1L6 的靶分子，我们使用表面等离子体共振分析了 OsBC1L6 与纤维六糖及其类似物的结合相互作用，确定纤维六糖与 OsBC1L6 结合。与野生型相比，OsBC1L6-RNAi 愈伤组织和 Tos 插入突变体缺失种子中的β-葡聚糖含量显著降低。这些发现表明，OsBC1L6 通过与种子成熟过程中质膜上的纤维素部分相互作用，调节胚乳细胞壁形成过程中的β-葡聚糖合成。
