Biology subjects

Ruan, Y.-L.

Publications and source records attributed to Ruan, Y.-L..

2 recordsLinked to original sources

bioRxiv2021

Hexose translocation mediated by SlSWEET5b is required for pollen maturation in Solanum lycopersicum

Pollen fertility is critical for successful fertilization and, accordingly, for crop yield. While sugar unloading affects growth and development of all types of sink organs, the molecular nature for sugar import to tomato pollen is poorly understood. However, SWEET transporters have been proposed to function in pollen development. Here, qRT-PCR revealed that SlSWEET5b was markedly expressed in flowers when compared to the remaining tomato SlSWEETs; particularly, in the stamens of maturing flower buds undergoing mitosis. Distinct accumulation of SlSWEET5b-GUS fusion proteins was present in mature flower buds, especially in anther vascular and inner cells, symplasmic isolated pollen cells and styles. The demonstration that GFP fusion proteins located to the plasma membrane support the idea that the SlSWEET5b carrier functions in apoplasmic sugar translocation during pollen maturation. Such function is in line with data from yeast complementation experiments and radiotracer uptakes, showing that SlSWEET5b operates as a low affinity hexose-specific passive facilitator, with a KM of ~36 mM. Most importantly, RNAi-mediated suppression of SlSWEET5b expression resulted in shrunken nucleus-less pollen cells, impaired germination and low seed yield. Interestingly, stamens from SlSWEET5b-silenced tomato mutants contained significantly lower amounts of sucrose and increased invertase activity, pointing to reduced carbon supply and perturbed sucrose homeostasis in this tissue. Taken together, our findings reveal an essential role of SlSWEET5b in mediating apoplasmic hexose import into phloem unloading cells and into developing pollen cells to support pollen mitosis and maturation in tomato flowers. One-sentence SummaryPlasma-membrane-localized SlSWEET5b facilitates a sequential hexose flux, from phloem to anther cells and from anther locule to pollen, to support pollen maturation and fertility in tomato flowers.

plant biology↗

bioRxiv2021

Zoom in on Ca2+ pattern and ion flux dynamics to decode spatial and temporal regulation of cotton fiber growth

Cotton fibers are single-celled trichomes initiated from ovule epidermis prior to anthesis. Thereafter, the fibers undergo rapid elongation for 20 d before switching to intensive cell wall cellulose synthesis. The final length attained determines fiber yield and quality. As such, cotton fiber represents an excellent single cell model to study regulation of cell growth and differentiation, with significant agronomical implications. One major unresolved question is whether fiber elongation follows a diffusive or a tip growth pattern. We addressed this issue by using cell biology and electrophysiological approaches. Confocal imaging of Ca2+ binding dye, fluo-3 acetoxymethyl (Fluo-3), and in situ microelectrode ion flux measurement revealed that cytosolic Ca2+ was evenly distributed along the elongating fiber cells with Ca2+ and H+ fluxes oscillating from apical to basal regions of the elongating fibers. These findings demonstrate that, contrary to growing pollen tubes or root hairs, cotton fiber growth follows a diffusive, but not the tip growth, pattern. Further analyses showed that the elongating fibers exhibited substantial net H+ efflux, indicating a strong activity of the plasma membrane H+-ATPase required for energy dependent solute uptake. Interestingly, the growing cotton fibers were responding to H2O2 treatment, know to promote fiber elongation, by a massive increase in the net Ca2+ and H+ efflux in both tip and basal zones, while non-growing cells lacked this ability. These observations suggest that desensitization of the cell and a loss of its ability to respond to H2O2 may be causally related to the termination of the cotton fiber elongation. One sentence summaryConfocal imaging of Ca2+ patterning and in situ microelectrode ion flux measurements demonstrate that, contrary to growing pollen tubes or root hairs, cotton fiber growth follows a diffusive, but not the tip growth, pattern.

cell biology↗