Xiao Yao, Ling Juanjuan, Yi Fei, Ma Wenjun, Lu Nan, Zhu Tianqing, Wang Junhui, Zhao Kun, Yun Huiling
State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of National Forestry and Grassland Administration, National Innovation Alliance of Catalpa bungei, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China.
Luoyang Academy of Agriculture and Forestry Sciences, Luoyang, China.
Front Plant Sci. 2021 Nov 15;12:704262. doi: 10.3389/fpls.2021.704262. eCollection 2021.
Lignin is a complex polymer in plant cell walls whose proportion is second only to that of cellulose and plays an important role in the mechanical properties of wood and stress resistance of plants. Here, we induced tension wood (TW) formation in by artificial bending and analyzed the lignin metabolism of the TW. LC-MS analysis showed that a significantly higher content of coniferyl aldehyde was observed in the TW cell wall than in the opposite wood (OW) and normal wood (NW) cell walls. TW had significantly lower contents of coniferyl alcohol than OW and NW. Raman spectroscopy results indicated that TW had lower total lignin than OW and NW. The transcription and translation levels of most of the differentially expressed genes (DEGs) involved in lignin monomer biosynthesis indicated upregulation in TW/OW and TW/NW. We found no significant difference in the transcription levels of three collision gases (CADs) between TW and OW or between NW, but their translation levels were significantly downregulated in TW, suggesting post-transcriptional control for . We predicted and analyzed transcription factors that could target DEGs involved in lignin monomer biosynthesis in TW. Based on the analysis of the relationships of targeting and coexpression, we found that NAC (evm.model.group1.695) could potentially target and , that HD-Zip (evm.model.group7.1157) had potential targeting relationships with , , and , and that their expression levels were significantly positive. It is speculated that the upregulation of NAC and HD-ZIP transcription factors activates the expression of downstream target genes, which leads to a significant increase in coniferyl aldehyde in TW. However, the decrease in total lignin in TW may be caused by the significant downregulation of CAD translation and the significant decrease in precursors (coniferyl alcohol). Whether the expression of CAD genes is regulated by post-transcriptional control and affects TW lignin metabolism needs further study.
木质素是植物细胞壁中的一种复杂聚合物，其比例仅次于纤维素，在木材的机械性能和植物抗逆性方面发挥着重要作用。在此，我们通过人工弯曲诱导[具体植物]形成张力木（TW），并分析了TW的木质素代谢。液相色谱-质谱联用（LC-MS）分析表明，TW细胞壁中松柏醛的含量显著高于对应木（OW）和正常木（NW）细胞壁。TW中松柏醇的含量显著低于OW和NW。拉曼光谱结果表明，TW的总木质素含量低于OW和NW。参与木质素单体生物合成的大多数差异表达基因（DEGs）的转录和翻译水平在TW/OW和TW/NW中呈上调。我们发现TW与OW之间或NW之间三种肉桂醇脱氢酶（CADs）的转录水平没有显著差异，但其翻译水平在TW中显著下调，表明存在转录后调控。我们预测并分析了可能靶向TW中参与木质素单体生物合成的DEGs的转录因子。基于靶向和共表达关系的分析，我们发现NAC（evm.model.group1.695）可能潜在靶向[具体基因1]和[具体基因2]，HD-Zip（evm.model.group7.1157）与[具体基因3]、[具体基因4]和[具体基因5]有潜在靶向关系，且它们的表达水平呈显著正相关。推测NAC和HD-ZIP转录因子的上调激活了下游靶基因的表达，导致TW中松柏醛显著增加。然而，TW中总木质素的减少可能是由于CAD翻译的显著下调和前体（松柏醇）的显著减少。CAD基因的表达是否受转录后调控影响TW木质素代谢需要进一步研究。
