KNAT2/6b, a class I KNOX gene, impedes xylem differentiation by regulating NAC domain transcription factors in poplar
KNAT2/6b, a class I KNOX gene, impedes xylem differentiation by regulating NAC domain transcription factors in poplar
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KNAT2/6b，I 类 KNOX 基因，通过调节杨树 NAC 域转录因子阻碍木质部分化
DOI：
10.1111/nph.16036
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发表时间：
2019-08-05
期刊：
影响因子：
9.4
通讯作者：
Lu, Meng-Zhu
中科院分区：
文献类型：
--
作者：
Zhao, Yanqiu;Song, Xueqin;Lu, Meng-Zhu
木质形成是木质部形成层母细胞分化的终末阶段，负调控因子在木质部分化过程中起着重要作用。研究了木质部分化负调控因子PagKNat2/6b的分子机制。PagKNA2/6b是在韧皮部和木质部高度表达的拟南芥KNA2和KNA6的同源基因。与非转基因对照相比，高表达PagKNA2/6b的转基因杨树植株的维管束模式发生了变化，表现为次生木质部减少，细胞壁较薄，含有较少的纤维素、木糖和木质素。RNA测序分析表明，差异表达基因具有丰富的木质部分化和次生壁合成功能。PagKNat2/6b下调NAM/ATAF/CUC(NAC)结构域基因PagSND_1-A1、PagSND_1-A2、PagSND_1-B2和PagVND6-C_1的表达，而PagXND1a则直接上调。因此，PagKNat2/6b的优势抑制形式通过下调PagXND1a导致单位茎粗木质部宽度的增加。PagKNA2/6b通过调控NAC结构域转录因子的表达，抑制杨树木材形成过程中的细胞分化和次生壁沉积。PagKNat2/6b直接激活PagXND1a是Knoxs木质部分化负调控网络中的关键节点。
Wood formation is the terminal differentiation of xylem mother cells derived from cambial initials, and negative regulators play important roles in xylem differentiation. The molecular mechanism of the negative regulator of xylem differentiation PagKNAT2/6b was investigated. PagKNAT2/6b is an ortholog of Arabidopsis KNAT2 and KNAT6 that is highly expressed in phloem and xylem. Compared to nontransgenic control plants, transgenic poplar plants overexpressing PagKNAT2/6b present with altered vascular patterns, characterized by decreased secondary xylem with thin cell walls containing less cellulose, xylose and lignin. RNA sequencing analyses revealed that differentially expressed genes are enriched in xylem differentiation and secondary wall synthesis functions. Expression of NAM/ATAF/CUC (NAC) domain genes including PagSND1-A1, PagSND1-A2, PagSND1-B2 and PagVND6-C1 is downregulated by PagKNAT2/6b, while PagXND1a is directly upregulated. Accordingly, the dominant repression form of PagKNAT2/6b leads to increased xylem width per stem diameter through downregulation of PagXND1a. PagKNAT2/6b can inhibit cell differentiation and secondary wall deposition during wood formation in poplar by modulating the expression of NAC domain transcription factors. Direct activation of PagXND1a by PagKNAT2/6b is a key node in the negative regulatory network of xylem differentiation by KNOXs.