刘贺
博士研究生
2023级博士研究生
职业履历
研究方向
木质素是次生细胞壁的重要成分。除了增强次生细胞壁的机械强度和疏水性之外，木质素还作为天然物理屏障抵御病原体入侵。按照该理论，木质素含量下降会干扰植物抗病性。然而，低木质素细胞壁也会介导抗病反应。在多种植物中发现，木质素合成关键酶的RNAi抑制植株或突变体抗病激素水杨酸积累，对病原菌的耐受性增强。然而，其中的信号转导分子机制还有待研究。
我们发现拟南芥编码木质素合成酶 CCR1（Cinnamoyl CoA Reductase 1）的功能缺失突变体与木质素单体合成酶HCT（hydroxycinnamoyl—CoA shikimate/quinate hydroxycinnamoyltranferase）的RNAi株系中，由于次生细胞壁木质素含量降低造成细胞壁发生重塑，在重塑过程中导致可溶性果胶类多糖的释放量增加。结合生化与遗传分析，发现这些果胶类多糖会被多聚半乳糖醛酸内切酶ADPG1 (Arabidopsis Dehiscence Zone Polygalacturonase 1)切割，产生果胶寡糖分子，并激活下游抗病反应。相关研究成果以并列第一作者发表在《PNAS》杂志（Gallego-Giraldo and Liu et al.,2020）。
在后续工作中，我们通过遗传筛选手段，根据植物体内抗病基因表达水平，筛选ccr1细胞壁防御信号抑制突变体。已分别鉴定到感知ccr1细胞壁变化的类受体激酶以及识别其寡糖信号的膜受体。并且从ADPG1的水解细胞壁的产物中鉴定到一个不同于已知的损伤相关分子模式的植物细胞壁寡糖分子，能够诱导抗病反应。
Wood formation, also known as xylogenesis, is the process through which a woody plant produces wood. It involves the differentiation and development of specialized cells called xylem cells, which comprise most of the plant's woody tissue.
Wood formation is a complex process that occurs in two main phases: primary growth and secondary growth. It is a fascinating area of study that requires a deep understanding of plant biology and molecular mechanisms.
Primary Growth: During primary growth, the primary xylem cells, such as the apical meristem, are produced in the growing tips of the plant. These cells elongate and differentiate into the primary xylem, which forms the initial framework for water and mineral transport within the plant. The primary xylem cells have thin cell walls and large lumens for efficient water movement.
Secondary Growth: In woody plants, secondary growth is responsible for the bulk of wood formation. It occurs in the vascular cambium, a layer of meristematic tissue located between the xylem and phloem. The vascular cambium produces new cells towards the stem or root's interior (xylem) and exterior (phloem).
• Secondary Xylem (Wood): The vascular cambium cells produced towards the interior differentiate into secondary xylem or wood. These cells are specialized for water conduction and structural support. They have thicker cell walls containing lignin, a polymer that provides strength and durability to wood. The secondary xylem cells accumulate in annual rings, forming a pattern that can be seen in a cross-section of a tree trunk.
• Secondary Phloem: The cells produced towards the exterior by the vascular cambium differentiate into secondary phloem. The secondary phloem is responsible for transporting sugars and other nutrients from the leaves to different plant parts.
Our group is at the forefront of** exploring the molecular basis of wood formation**. This involves studying the genes, proteins, and molecular mechanisms that regulate the processes of cell differentiation, cell division, cell wall biosynthesis, and other biochemical pathways involved in wood development. Our research has the potential to revolutionize tree breeding efforts, aiding in the development of faster-growing, resilient, and high-quality trees.
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