Plasma Membrane-Associated SCAR Complex Subunits Promote Cortical F-Actin Accumulation and Normal Growth Characteristics in Arabidopsis Roots

The ARP2/3 complex, a highly conserved nucleator of F-actin polymerization, and its activator, the SCAR complex, have been shown to play important roles in leaf epidermal cell morphogenesis in Arabidopsis. However, the intracellular site（s） and function（s） of SCAR and ARP2/3 complex-dependent actin polymerization in plant cells remain unclear. We demonstrate that putative SCAR complex subunits BRK1 and SCAR1 are localized to the plasma membrane at sites of cell growth and wall deposition in expanding cells of leaves and roots. BRK1 localization is SCAR-dependent, providing further evidence of an association between these proteins in vivo. Consistent with plasma membrane localization of SCAR complex subunits, cortical F-actin accumulation in root tip cells is reduced in brkl mutants. Moreover, mutations disrupting the SCAR or ARP2/3 complex reduce the growth rate of roots and their ability to penetrate semi-solid medium, suggesting reduced rigidity. Cell walls of mutant roots exhibit abnormal structure and composition at intercellular junctions where BRK1 and SCAR1 are enriched in the adjacent plasma membrane. Taken together, our results suggest that SCAR and ARP2/3 complex-dependent actin polymerization promotes processes at the plasma membrane that are important for normal growth and wall assembly.

“学习投入”说辞与学生心声:后新冠时代数字实践中的互联、质疑和包容

由于实行公共卫生“封锁”措施,新冠危机导致全球高等教育应急转而开展在线教学,组织学生在线学习。在英国,2020年3月的这场转变突如其来,各大学几乎没有时间准备,而且很多大学是在培训和经验都不充足的情况下被迫将其教学转为数字模式。随后,高等教育机构把提升数字教育质量摆在首位,推出各种战略举措和为教职员工提供培训活动。本文由师生合作撰写,报告在英国一所大型研究型大学进行的两项研究的情况。这两项研究获得机构支持,旨在探索新冠危机期间学生在线学习的体验和最为关切的问题。我们在讨论研究结果时认为,学生的看法与主流对一些问题的假设不尽一致,如学生“包容性”、在线学术“社区”和鼓励“质疑”的教学。因此我们必须更加深入思考何为有意义和丰富的在线教育体验。本着从新冠大流行中“吸取教训”的精神,本文另辟蹊径思考这些价值观,强调关系、社区、差异和关爱之心的重要性。文章最后讨论研究发现以及研究发现对后新冠大流行背景下理论、研究、政策和实践的启示,提出关爱之心应该被视为发展数字教育以及促进学生学习投入实践和道德规范的核心。