Functional Characterisation of the Poplar Atypical Aspartic Protease Gene PtAP66 in Wood Secondary Cell Wall Deposition
Functional Characterisation of the Poplar Atypical Aspartic Protease Gene PtAP66 in Wood Secondary Cell Wall Deposition
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杨树非典型天冬氨酸蛋白酶基因 PtAP66 在木材次生细胞壁沉积中的功能表征
DOI：
10.3390/f12081002
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发表时间：
2021-08-01
期刊：
影响因子：
2.9
通讯作者：
Yang, Chuanping
中科院分区：
文献类型：
--
作者：
Cao, Shenquan;Wang, Cong;Yang, Chuanping
次生细胞壁的沉积是木材形成过程中的一个重要过程。虽然天冬氨酸蛋白水解酶(AP)在草本植物中具有调节作用，但非典型AP参与树木SCW沉积的研究尚未见报道。在本研究中，我们研究了毛果杨非典型AP基因PtAP66，该基因与木材SCW沉积有关。来自AspWood资源的转录组数据显示，在毛果杨次生木质部中，PtAP66的转录本从维管形成层增加到木质部细胞扩张区，并在SCW形成区保持较高水平。来自转基因拟南芥植物根和瞬时转化三果树叶片原生质体的荧光信号强烈表明，PtAP66融合荧光蛋白(PtAP66-GFP或PtAP66-YFP)定位于质膜。扫描电子显微镜(SEM)显示，与野生型植物相比，Cas9/gRNA诱导的PtAP66突变体的次生木质部纤维的SCW厚度减小。此外，木材成分分析表明，突变株的纤维素含量降低了4.90-5.57%。转录分析进一步表明，PtAP66的缺失下调了几个与SCW合成相关的基因的表达，包括纤维素和半纤维素合成酶编码基因。综上所述，这些发现表明，非典型的PtAP66在木材形成过程中的SCW沉积中起着重要作用。
Secondary cell wall (SCW) deposition is an important process during wood formation. Although aspartic proteases (APs) have been reported to have regulatory roles in herbaceous plants, the involvement of atypical APs in SCW deposition in trees has not been reported. In this study, we characterised the Populus trichocarpa atypical AP gene PtAP66, which is involved in wood SCW deposition. Transcriptome data from the AspWood resource showed that in the secondary xylem of P. trichocarpa, PtAP66 transcripts increased from the vascular cambium to the xylem cell expansion region and maintained high levels in the SCW formation region. Fluorescent signals from transgenic Arabidopsis plant roots and transiently transformed P. trichocarpa leaf protoplasts strongly suggested that the PtAP66-fused fluorescent protein (PtAP66-GFP or PtAP66-YFP) localised in the plasma membrane. Compared with the wild-type plants, the Cas9/gRNA-induced PtAP66 mutants exhibited reduced SCW thickness of secondary xylem fibres, as suggested by the scanning electron microscopy (SEM) data. In addition, wood composition assays revealed that the cellulose content in the mutants decreased by 4.90–5.57%. Transcription analysis further showed that a loss of PtAP66 downregulated the expression of several SCW synthesis-related genes, including cellulose and hemicellulose synthesis enzyme-encoding genes. Altogether, these findings indicate that atypical PtAP66 plays an important role in SCW deposition during wood formation.