Department of Arctic and Marine Biology, UiT the Arctic University of Norway, Tromsø, 9037, Norway; The Arctic Centre for Sustainable Energy, UiT the Arctic University of Norway, Tromsø, 9037, Norway.
Department of Arctic and Marine Biology, UiT the Arctic University of Norway, Tromsø, 9037, Norway.
Plant Physiol Biochem. 2024 May;210:108633. doi: 10.1016/j.plaphy.2024.108633. Epub 2024 Apr 17.
Cuscuta campestris is a common and problematic parasitic plant which relies on haustoria to connect to and siphon nutrients from host plants. Glycoside hydrolase family 9 (GH9) cellulases (EC 3.2.1.4) play critical roles in plant cell wall biosynthesis and disassembly, but their roles during Cuscuta host invasion remains underexplored. In this study, we identified 22 full-length GH9 cellulase genes in C. campestris genome, which encoded fifteen secreted and seven membrane-anchored cellulases that showed distinct phylogenetic relationships. Expression profiles suggested that some of the genes are involved in biosynthesis and remodeling of the parasite's cell wall during haustoriogenesis, while other genes encoding secreted B- and C-type cellulases are tentatively associated with degrading host cell walls during invasion. Transcriptomic data in a host-free system and in the presence of susceptible or partially resistant tomato hosts, showed for especially GH9B7, GH9B11 and GH9B12 a shift in expression profiles in the presence of hosts, being more highly expressed during host attachment, indicating that Cuscuta can tune cellulase expression in response to a host. Functional analyses of recombinant B- and C-type cellulases showed endoglucanase activities over wide pH and temperature conditions, and activities towards multiple cellulose and hemicellulose substrates. These findings improve our understanding of host cell wall disassembly by Cuscuta, and cellulase activity towards broad substrate range potentially explain its wide host range. This is the first study to provide a broad biochemical insight into Cuscuta GH9 cellulases, which based on our study may have potential applications in industrial bioprocessing.
菟丝子是一种常见且具有危害性的寄生植物，它依靠吸器与宿主植物相连，并从中吸取养分。糖苷水解酶家族 9（GH9）纤维素酶（EC 3.2.1.4）在植物细胞壁的生物合成和分解中起着关键作用，但它们在菟丝子宿主入侵过程中的作用仍未得到充分探索。在本研究中，我们在菟丝子基因组中鉴定出 22 个全长 GH9 纤维素酶基因，这些基因编码了 15 个分泌型和 7 个膜锚定型纤维素酶，它们具有明显的系统发育关系。表达谱分析表明，其中一些基因参与了寄生细胞壁在吸器形成过程中的生物合成和重塑，而其他编码分泌型 B 型和 C 型纤维素酶的基因则可能与入侵过程中宿主细胞壁的降解有关。在无宿主系统和存在易感或部分抗性番茄宿主的情况下的转录组数据表明，特别是 GH9B7、GH9B11 和 GH9B12，在有宿主存在的情况下表达谱发生了变化，在宿主附着时表达水平更高，这表明菟丝子可以根据宿主的情况调节纤维素酶的表达。重组 B 型和 C 型纤维素酶的功能分析表明，它们在广泛的 pH 和温度条件下具有内切葡聚糖酶活性，并且能够作用于多种纤维素和半纤维素底物。这些发现提高了我们对菟丝子宿主细胞壁分解的理解，纤维素酶对广泛的底物范围的活性可能解释了它广泛的宿主范围。这是首次对菟丝子 GH9 纤维素酶进行广泛的生化研究，根据我们的研究，这些酶可能在工业生物加工中有潜在的应用。
