Biology subjects

Wu, S.-Z.

Publications and source records attributed to Wu, S.-Z..

5 recordsLinked to original sources

bioRxiv2026

The Sulfated PSY Peptide Negatively Regulates Receptor Kinase Activity to Promote Growth

Complex signaling pathways organize cell expansion and proliferation across cells to pattern tissues and organs in plants. The sulfotyrosine peptide hormone family, PLANT PEPTIDE CONTAINING SULFATED TYROSINE (PSY), contributes to these processes. We identified two plasma membrane-localized receptors, PSYR1 and PSYR2, that are necessary for PSY signaling and regulate growth in Physcomitrium patens. Membrane-associated PSYRs accumulate to high levels in a mutant lacking TYROSYL PROTEIN SULFOTRANSFERASE (TPST). Given that a tpst null mutant ({triangleup}tpst) is impaired in sulfation, this suggests that in the absence of sulfated peptides, PSYRs accumulate on the membrane. A null mutant of the PSY receptors,{triangleup} psyr1/2, showed increased growth and was epistatic to{triangleup} tpst, suppressing defects in gametophore formation and early senescence. The transcriptional profiles comparing wild type to{triangleup} psyr1/2 and{triangleup} psyr1/2/{triangleup}tpst showed 25 to 30 differentially expressed genes between the receptor null mutants and wild type, with a common signature of cell wall remodeling and stress responses. Similarly, a PSYR1 kinase-inactive mutation rescued{triangleup} tpst and relieved the accumulation of membrane-associated PSYRs. In contrast, overexpression of PSYRs inhibited plant growth, with phenotypic severity correlating with the amount of overexpression. These data are consistent with a constitutive activation model in which membrane-associated PSYRs unbound to PSY serve to inhibit growth through an active kinase. In the presence of the PSY peptide, the kinase is inactivated, promoting growth and driving PSY expression. The relationship between growth-repressive PSYR kinase activity and growth-promoting PSYR kinase inactivation in P. patens serves as a model for optimizing plant growth and development.

plant biology↗

bioRxiv2026

Septin-mediated coupling of protein import and division during chloroplast evolution

Chloroplast biogenesis depends on both protein import and organelle division, yet how their coordination emerged during evolution remains unclear. Here, we show that the single septin SEP1 links these pathways in the green alga Chlamydomonas reinhardtii. SEP1 forms a filamentous network on the chloroplast envelope during interphase and reorganizes into a ring at the chloroplast division site during cytokinesis. Loss of SEP1 selectively impairs import of chloroplast-division proteins and causes mispositioning of the division ring, without impairing bulk chloroplast protein import. SEP1 physically associates with outer-envelope TOC GTPases through evolutionarily related GTPase domains. Phylogenetic analysis places TOC GTPases within an algal septin-derived clade, and heterologous expression of SEP1 in land plants, in which septins are absent, shows conservation of its chloroplast targeting and TOC binding. Together, these findings identify septins as coordinators of plastid protein import and division and suggest that this coupling emerged early in chloroplast evolution.

cell biology↗

bioRxiv2025

Evidence for Early Evolution of Sulfated Peptide Signaling in Plant Development

In plants, the cell wall fixes the position of each cell; therefore, during development, plants rely on cellular proliferation and expansion for tissue patterning and organ formation. How plant cells communicate with neighboring cells to coordinate expansion for properly patterned tissues and organs is not well understood. In seed plants, organ growth is known to be modulated by sulfotyrosyl peptide signaling. Here, we report that the activity of TYROSYL PROTEIN SULFOTRANSFERASE (TPST), which is responsible for the post-translational modification of sulfotyrosyl peptides, is essential for expansion during development in the non-vascular plant, Physcomitrium patens. Plants that harbor a null mutation in the gene encoding TPST ({Delta}tpst) were smaller, formed fewer caulonemal filaments, and were unable to form expanded gametophores. In {Delta}tpst multiple aspects of gametophore development were affected, including the first division of the gametophore initial, as well as reduced rates of cell division and expansion. Mutational analysis of P. patens TPST identified the residue Histidine 124, a candidate catalytic residue, as essential for TPST function. Notably, addition of the sulfated signaling peptide, PSY1 from either P. patens or Arabidopsis thaliana, rescued all {Delta}tpst developmental deficits. Taken together, these data suggest that TPST functions to sulfate PSY, and this activity is necessary for plant growth and development. Furthermore, since addition of AtPSY fully rescues {Delta}tpst and PpPSY promotes root elongation in Arabidopsis and rice, these findings suggest that PSY signaling is evolutionarily conserved.

developmental biology↗

bioRxiv2021

Cellulose synthase-like D (CSLD) proteins move in the plasma membrane and their targeting to cell tips, but not cell plates, depends on the actin cytoskeleton

Cellulose Synthase-Like D (CSLD) proteins are implicated in cell wall remodeling during tip growth and cell division in plants, and are known to generate {beta}-1,4-glucan. It is unknown whether they form complexes and move in the plasma membrane like members of the Cellulose Synthase (CESA) family. We used the genetically tractable moss Physcomitrium patens, which has a filamentous protonemal stage that undergoes both tip growth and cell division and is amenable to high resolution live cell imaging, to investigate CSLD function and intracellular trafficking. CSLD2 and CSLD6 are highly expressed in gametophores and are redundantly required for gametophore cellular patterning. Live cell imaging revealed that CSLD6 is also expressed in protonemata where it moves in the plasma membrane and localizes to cell plates and cell tips. Notably, delivery to the apical plasma membrane, but not the cell plate, depends on actin. By comparing the behavior of endogenously tagged CSLD6 and CESA10, we discovered that CSLD6 movements in the plasma membrane were significantly faster, shorter in duration and less linear than CESA10 movements and were insensitive to the cellulose synthesis inhibitor isoxaben. These data suggest that CSLD6 and CESA10 function within different structures and may thus produce structurally distinct cellulose microfibrils.

plant biology↗

bioRxiv2020

The COPII components Sec23 and Sec24 form isoform specific subcomplexes with Sec23D/E and Sec24C/D essential for tip growth

COPII, a coat of proteins that form vesicles on the ER, mediates vesicle traffic from the ER to the Golgi. In contrast to metazoans that have few genes encoding each COPII component, plants have expanded these gene families leading to the hypothesis that plant COPII has functionally diversified. Here, we analyzed the gene families encoding for the Sec23/24 heterodimer in the moss Physcomitrium (Physcomitrella) patens. In P. patens, Sec23 and Sec24 gene families are each comprised of seven genes. Silencing the Sec23/24 genes revealed isoform specific contributions to polarized growth, with the closely related Sec23D/E and Sec24C/D essential for protonemal development. Focusing on the Sec23 gene family, we discovered that loss of Sec23D alters ER morphology, increases ER stress, inhibits trafficking to the Golgi and to the plasma membrane in tip growing protonemata. In contrast, the remaining five Sec23 genes are dispensable for tip growth. While Sec23A/B/C/F/G do not quantitatively affect ER to Golgi trafficking in protonemata, they do contribute to secretion to the plasma membrane. Of the three highly expressed Sec23 isoforms in protonemata, Sec23G forms ER exit sites that are larger than Sec23B and Sec23D and do not overlap with Sec23D. Furthermore, ER exit sites labeled by Sec23B or Sec23G form in the absence of Sec23D. These data suggest that Sec23D/E form unique ER exit sites contributing to secretion that is essential for tip growing protonemata.

cell biology↗