Laboratory for Plant Development
Graduate School of Science, Osaka University
Recent and current research
Lateral root formation
Lateral root formation is an excellent model system for research of self-organization. The lateral root formation is initiated from pericycle cells. An auxin peak is spontaneously created in the pericycle and drives asymmetric cell division. The auxin gradient plays a central role in primordial organization.
The pericycle cells have special characters. They can spontaneously create auxin peaks, and they undergo cell division in response to auxin. Even external addition of a high level of auxin induces cell division exclusively in the pericycle. We found that pairs of bHLH transcription factors (PFA/PFB dimers) determine the pericycle identity, including its competence to undergo auxin-induced cell division (Ye Zhang……Tatsuo Kakimoto, Nature Plants, 2021).
Please see the press release for a little more detailed explanation in Japanese. 🔗
We are working on PFA/PFB targets. We are also working on intercellular communication that enable primordial formation.
Vascular development
Water is transported through xylem and is transpirated from the stomata. We found that CLE9/10 peptide (the same peptide is produced from two genes, CLE9 and CLE10) regulate development of xylem and stomata. This peptide negatively regulates the number of xylem files through BAM receptor–CIK coreceptor complexes and stomata through HSL1 receptor–SERK coreceptors (Quian et al, Nature Plants 2018).
Please see the press release for a little more detailed explanation in Japanese. 🔗
The phloem consists of two types of cells, sieve elements and companion cells. The sieve elements lack nuclei but are living with the support of companion cells. We found that Dof transcription factors preferentially expressed in the phloem (phloem-Dofs) precursors are necessary and sufficient for the formation of the sieve elements and companion cells. While phloem-Dofs induce genes necessary for the formation of phloem cells, they induced CLE25, 26 and 45. CLE25/26/45 are diffusible peptides, perceived by BAM receptor–CIK coreceptor complexes, and downregulates phloem-Dof proteins. This feedback loop restricts the phloem differentiation to the proper phloem region (Qian et al., Nature Plants 2022).
Please see the press release for a little more detailed explanation in Japanese. 🔗
Current research and future development: Phloem-Dof transcription factors are transcription factors that can induce the formation of sieve tubes and companion cells. We are investigating the function of genes controlled by Phloem-Dof. We have shown that CLE25/26/45 act as lateral inhibitors during phloem formation and suppress the expansion of the phloem region. .
Mechanism of cell polarity control
G protein is a protein that acts as a molecular switch by taking GTP-bound form and GDP-bound form. In particular, Rho-type G proteins are involved in the regulation of cell division and cell polarity in animals and plants. Plant Rho-type GTP-binding proteins are called Rho of Plants (ROP). We found that the RIP proteins, which binds to activated ROPs, are involved in regulating the direction of cell division in plant leaves and thus leaf shape (Plant Cell Physiology, 2022).
Arabidopsis thaliana has five genes encoding RIP proteins, and we found that all of these RIP proteins bind to microtubules in fusion experiments with GFP. In plants (rip1/2/3/4/5) in which all five RIP genes were disrupted, the movements of polymerizing ends of microtubules were accelerated. The preprophase band (PPB) of microtubules is formed before mitosis and mark the future cell division plane position. We found that the PPB in the longitudinal direction of the leaves decreased In rip1/2/3/4/5, and as a result cell number in the transverse axis was decreased resulting in thin leaves.
Please see the press release for a little more detailed explanation in Japanese. 🔗
Current research and future development: We are examining the possible roles of ROPs and their regulators in cell division plane control.
