Populus NST/SND orthologs are key regulators of secondary cell wall formation in wood fibers, phloem fibers and xylem ray parenchyma cells
Populus NST/SND orthologs are key regulators of secondary cell wall formation in wood fibers, phloem fibers and xylem ray parenchyma cells
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DOI：
10.1093/treephys/tpz004
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发表时间：
2019-04-01
期刊：
影响因子：
4
通讯作者：
Taniguchi, Toru
中科院分区：
文献类型：
--
作者：
Takata, Naoki;Awano, Tatsuya;Taniguchi, Toru
木质纤维在木质部组织中形成较厚的次生细胞壁，为树木提供机械支撑。NAC次生壁增厚促进因子3/次生壁相关NAC结构域蛋白1（NST 3/SND 1）和NST 1被鉴定为模式植物拟南芥木质部纤维细胞中SCW形成的主要调节因子。在杨属物种中，四个NST/SND直向同源物已经被保守并协调控制木材纤维和韧皮部纤维中SCW的形成。然而，它仍然有待阐明是否SCW的形成在其他木质部细胞，如射线薄壁细胞和导管分子，在白杨NST/SND直系同源调控。我们使用成簇规则间隔短回文重复序列（CRISPR）/CRISPR相关蛋白9核酸酶（Cas9）系统敲除杂交白杨中的所有NST/SND基因，并研究敲除突变体中茎组织的详细组织学外观。光学显微镜和透射电镜观察表明，敲除突变体的木质纤维、韧皮部纤维和木质射线薄壁细胞中的SCW受到严重抑制。虽然几乎所有的木材纤维缺乏SCW，但一些纤维细胞形成厚的细胞壁。不规则的细胞壁形成纤维保留了初生壁和SCW，主要分布在血管分子附近。场发射扫描电镜观察表明，敲除突变体中不规则SCW形成木纤维与野生型中正常木纤维的纹孔结构特征如形状和大小没有明显差异。细胞壁组分，如纤维素，半纤维素和木质素沉积在细胞壁的不规则SCW形成木材纤维的四倍体突变体。我们的研究结果表明，四个NST/SND直系同源物是SCW形成的主开关在木材纤维，木质射线薄壁细胞和韧皮部纤维在白杨，而SCW仍然形成有限的木材纤维，这是位于附近区域的导管元件敲除突变体。
Wood fibers form thick secondary cell wall (SCW) in xylem tissues to give mechanical support to trees. NAC SECONDARY WALL THICKENING PROMOTING FACTOR3/SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN 1 (NST3/SND1) and NST1 were identified as master regulators of SCW formation in xylem fiber cells in the model plant Arabidopsis thaliana. In Populus species, four NST/SND orthologs have been conserved and coordinately control SCW formation in wood fibers and phloem fibers. However, it remains to be elucidated whether SCW formation in other xylem cells, such as ray parenchyma cells and vessel elements, is regulated by NST/SND orthologs in poplar. We knocked out all NST/SND genes in hybrid aspen using the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 nuclease (Cas9) system and investigated the detailed histological appearance of stem tissues in the knockout mutants. Observation by light microscopy and transmission electron microscopy showed that SCW was severely suppressed in wood fibers, phloem fibers and xylem ray parenchyma cells in the knockout mutants. Although almost all wood fibers lacked SCW, some fiber cells formed thick cell walls. The irregularly cell wall-forming fibers retained primary wall and SCW, and were mainly located in the vicinity of vessel elements. Field emission-scanning electron microscope observation showed that there were no apparent differences in the structural features of pits such as the shape and size between irregularly SCW-forming wood fibers in the knockout mutants and normal wood fibers in wildtype. Cell wall components such as cellulose, hemicellulose and lignin were deposited in the cell wall of irregularly SCW-forming wood fibers in quadruple mutants. Our results indicate that four NST/SND orthologs are master switches for SCW formation in wood fibers, xylem ray parenchyma cells and phloem fibers in poplar, while SCW is still formed in limited wood fibers, which are located at the region adjacent to vessel elements in the knockout mutants.