KNAT7 regulates xylan biosynthesis in Arabidopsis seed-coat mucilage
KNAT7 regulates xylan biosynthesis in Arabidopsis seed-coat mucilage
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KNAT7 调节拟南芥种皮粘液中的木聚糖生物合成
DOI：
10.1093/jxb/eraa189
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发表时间：
2020-07-06
影响因子：
6.9
通讯作者：
Hu, Ruibo
中科院分区：
文献类型：
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作者：
Wang, Yiping;Xu, Yan;Hu, Ruibo
木聚糖作为植物细胞壁的主要半纤维素成分，在维持细胞壁结构方面起着决定性的作用。然而，木聚糖生物合成的转录调控机制在很大程度上仍然未知。拟南芥种子粘液是研究植物细胞壁多糖生物合成和修饰的理想系统。在这里，我们确定结拟南芥7（KNAT 7）作为种子粘液木聚糖生物合成的正转录调节因子。在knat 7 -3突变体的粘液中，木聚糖含量显著降低，并且这伴随着木聚糖生物合成相关基因不规则木质素14（IRX 14）和MUCILAGE MODIFIED 5/MUCILAGE RELATED 21（MUM 5/MUCI 21）的表达显著降低。电泳迁移率变动分析、酵母单杂交分析和染色质免疫沉淀与定量PCR证实了KNAT 7与IRX 7、IRX 14和MUM 5/MUCI 21启动子中的KNOTTED 1（KN 1）结合位点[KBS，TGACAG（G/C）T]的直接结合。此外，在叶肉原生质体中的反式激活测定中，KNAT 7直接激活IRX 14和MUM 5/MUCI 21的表达，并且在knat 7 -3中过表达IRX 14或MUM 5/MUCI 21部分地挽救了粘液粘附的缺陷。综上所述，我们的结果表明，KNAT 7正调控木聚糖生物合成的种皮粘液通过直接激活的表达IRX 14和MUM 5/MUCI 21。
As a major hemicellulose component of plant cell walls, xylans play a determining role in maintaining the wall structure. However, the mechanisms of transcriptional regulation of xylan biosynthesis remain largely unknown. Arabidopsis seed mucilage represents an ideal system for studying polysaccharide biosynthesis and modifications of plant cell walls. Here, we identify KNOTTED ARABIDOPSIS THALIANA 7 (KNAT7) as a positive transcriptional regulator of xylan biosynthesis in seed mucilage. The xylan content was significantly reduced in the mucilage of the knat7-3 mutant and this was accompanied by significantly reduced expression of the xylan biosynthesis-related genes IRREGULAR XYLEM 14 (IRX14) and MUCILAGE MODIFIED 5/MUCILAGE-RELATED 21 (MUM5/MUCI21). Electrophoretic mobility shift assays, yeast one-hybrid assays, and chromatin immunoprecipitation with quantitative PCR verified the direct binding of KNAT7 to the KNOTTED1 (KN1) binding site [KBS,TGACAG(G/C)T] in the promoters of IRX7, IRX14, and MUM5/MUCI21 in vitro, in vivo, and in planta. Furthermore, KNAT7 directly activated the expression of IRX14 and MUM5/MUCI21 in transactivation assays in mesophyll protoplasts, and overexpression of IRX14 or MUM5/MUCI21 in knat7-3 partially rescued the defects in mucilage adherence. Taken together, our results indicate that KNAT7 positively regulates xylan biosynthesis in seed-coat mucilage via direct activation of the expression of IRX14 and MUM5/MUCI21.