Department of Biology, The Pennsylvania State University, University Park, PA, United States of America.
Institute of Grassland and Environmental Research, Aberystwyth, United Kingdom.
PLoS One. 2020 Oct 9;15(10):e0240369. doi: 10.1371/journal.pone.0240369. eCollection 2020.
While many aspects of the growth of maize are well understood, the role of cell wall feruloylation particularly during internode elongation has not been firmly established, but results so far indicate that it has significant implications for both biofuel feedstock conversion and for crop yield. The growth of the cell wall is achieved by synthesis, integration and cross-linking between wall polymers. As ferulate oxidative coupling of arabinoxylan side chains constitutes a significant type of cross-link in grass cell walls, it is expected to have a crucial role in plant growth. Making use of plants expressing an apoplast targeted Aspergillus niger FAEA under the control of either a constitutive or an inducible promoter, the role of cell wall feruloylation in maize internode expansion was investigated. Analysis of FAEA expressing plants showed that where FAEA was targeted to the apoplast under a constitutive promoter, plants varied in stature either from semi-dwarf plants with a 40-60% height reduction, to extreme dwarf mutants with over 90% reduction in plant heights compared to controls. Results indicate that disruption of cell wall feruloylation by FAEA occurs before the start of rapid internode expansion is initiated and affects the normal course of internode elongation, resulting in short internodes and dwarfed plants. In contrast, when under the inducible Lm See1 senescence promoter, FAEA activity was found to be low up to the VT stage of development but increased significantly at the VR stage as plants began to senesce, strongly suggesting that normal cell wall feruloylation is required for the process of internode expansion. In addition, with apoplast targeted expression of FAEA under control of the senescence enhanced promoter it was possible to demonstrate decreased cell wall feruloylation without affecting internode expansion or other aspects of plant development.
虽然玉米生长的许多方面都得到了很好的理解，但细胞壁阿魏酰化在节间伸长过程中的作用尚未得到明确证实，但迄今为止的结果表明，它对生物燃料原料转化和作物产量都有重要意义。细胞壁的生长是通过细胞壁聚合物的合成、整合和交联来实现的。由于阿魏酸氧化偶联阿拉伯木聚糖侧链构成了草类细胞壁中重要的交联类型，因此它有望在植物生长中发挥关键作用。利用在组成型或诱导型启动子控制下表达质外体靶向的黑曲霉 FAEA 的植物，研究了细胞壁阿魏酰化在玉米节间伸长中的作用。表达 FAEA 的植物分析表明，当 FAEA 在组成型启动子的控制下靶向质外体时，植物的高度变化从半矮化植物的高度降低 40-60%，到极度矮化突变体的高度降低超过 90%，与对照相比。结果表明，FAEA 通过破坏细胞壁阿魏酰化发生在快速节间伸长开始之前，并影响节间伸长的正常过程，导致节间缩短和植物矮化。相比之下，当处于诱导型 Lm See1 衰老启动子下时，FAEA 活性在发育的 VT 阶段之前一直较低，但在 VR 阶段随着植物开始衰老而显著增加，这强烈表明正常的细胞壁阿魏酰化是节间伸长过程所必需的。此外，通过衰老增强启动子控制的质外体靶向表达 FAEA，可以在不影响节间伸长或植物发育其他方面的情况下，降低细胞壁阿魏酰化。
