Basally distributed actin array drives embryonic hypocotyl elongation during the seed-to-seedling transition in Arabidopsis.

Xuan Cui, Minxia Zou, Jiejie Li

The New phytologist 2023 Oct

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Seed germination is a vital developmental transition for the production of progeny by sexual reproduction in spermatophytes. The seed-to-seedling transition is predominately driven by hypocotyl cell elongation. However, the mechanism that underlies hypocotyl growth remains largely unknown. In this study, we characterized the actin array reorganization in embryonic hypocotyl epidermal cells. Live-cell imaging revealed a basally organized actin array formed during hypocotyl cell elongation. This polarized actin assembly is a barrel-shaped network, which comprises a backbone of longitudinally aligned actin cables and a fine actin cap linking these cables. We provide genetic evidence that the basal actin array formation requires formin-mediated actin polymerization and directional movement of actin filaments powered by myosin XIs. In fh1-1 and xi3ko mutants, actin filaments failed to reorganize into the basal actin array, and the hypocotyl cell elongation was inhibited compared with wild-type plants. Collectively, our work uncovers the molecular mechanisms for basal actin array assembly and demonstrates the connection between actin polarization and hypocotyl elongation during seed-to-seedling transition. © 2023 The Authors New Phytologist © 2023 New Phytologist Foundation.

Citation

Xuan Cui, Minxia Zou, Jiejie Li. Basally distributed actin array drives embryonic hypocotyl elongation during the seed-to-seedling transition in Arabidopsis. The New phytologist. 2023 Oct;240(1):191-206