Yoko Mizuta
Assistant Professor, Principal Invesitigator, WPI-ITbM, Nagoya University

Lecture Title

Deep imaging reveals dynamics and signaling in one-to-one pollen tube guidance

Abstract

Flowers are the reproductive organs of angiosperms. The sperm cells of the angiosperms have lost their motility to evolution and require the pollen tube to be delivered to the ovule, which is deeply embedded in the pistil base. To ensure successful fertilization, angiosperms have evolved mechanisms for pollen–pistil interactions involving chemotropic guidance system known as “pollen tube guidance.” In the flower of Arabidopsis thaliana, ovule-derived chemoattractants can affect all pollen tubes, it is thought that an ovule can potentially attract multiple pollen tubes. However, such case is rare, despite the presence of many ovules and pollen tubes. This “one-to-one” guidance contributes to polyspermy blocking and efficient seed production, whereas the functional mechanisms underlying the directional cues and polytubey blocks in the depths of the pistil remain unknown. We developed a two-photon live imaging method to directly observe pollen tube guidance in the pistil of A. thaliana, clarifying signaling and cellular behaviors in the one-to-one guidance. Not only receptor-like kinase FERONIA in the septum, but ovular gametophytic FERONIA and GPI-anchored protein LORELEI, as well as FERONIA- and LORELEI-independent repulsion signal, are involved in polytubey blocks on the ovular funiculus. These funicular blocks are not strictly maintained in the first 45 min, explaining previous reports of polyspermy in flowering plants. Our live imaging also revealed the novel repulsion process of excess pollen tubes on the funiculus. We are also investigating the development of new plant breeding technologies for pollen tube-mediated genome editing and male germline regulation. These studies may provide insights into the molecular basis of sexual plant reproduction that will accelerate plant breeding and enrich our lives by increasing food production.

Reference

  1. Yoko Mizuta, Daigo Sakakibara, Shiori Nagahara, Ikuma Kaneshiro, Takuya T Nagae, Daisuke Kurihara, and Tetsuya Higashiyama. Deep imaging reveals dynamics and signaling in one-to-one pollen tube guidance. EMBO reports. 25: 2529 - 2549, 2024. DOI: 10.1038/s44319-024-00151-4
  2. Ikuma Kaneshiro, Masako Igarashi, Tetsuya Higashiyama, and Yoko Mizuta. Target pollen isolation using automated infrared laser-mediated cell disruption. Quantitative Plant Biology 3, 2022. DOI: 10.1017/qpb.2022.24
  3. Shiori Nagahara, Tetsuya Higashiyama, and Yoko Mizuta. Detection of a biolistic delivery of fluorescent markers and CRISPR/Cas9 to the pollen tube. Plant Reproduction. 34: 191-205, 2021. DOI: 10.1007/s00497-021-00418-z

Mizuta Group webpage

https://www.itbm.nagoya-u.ac.jp/en/members/group/y-mizuta.php