Biology subjects

Ko, H.-Y.

Publications and source records attributed to Ko, H.-Y..

3 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

Vaccinia virus-based vaccines confer protective immunity against SARS-CoV-2 virus in Syrian hamsters

COVID-19 in humans is caused by Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) that belongs to the beta family of coronaviruses. SARS-CoV-2 causes severe respiratory illness in 10-15% of infected individuals and mortality in 2-3%. Vaccines are urgently needed to prevent infection and to contain viral spread. Although several mRNA- and adenovirus-based vaccines are highly effective, their dependence on the "cold chain" transportation makes global vaccination a difficult task. In this context, a stable lyophilized vaccine may present certain advantages. Accordingly, establishing additional vaccine platforms remains vital to tackle SARS- CoV-2 and any future variants that may arise. Vaccinia virus (VACV) has been used to eradicate smallpox disease, and several attenuated viral strains with enhanced safety for human applications have been developed. We have generated two candidate SARS-CoV-2 vaccines based on two vaccinia viral strains, MVA and v-NY, that express full-length SARS-CoV-2 spike protein. Whereas MVA is growth-restricted in mammalian cells, the v-NY strain is replication-competent. We demonstrate that both candidate recombinant vaccines induce high titers of neutralizing antibodies in C57BL/6 mice vaccinated according to prime-boost regimens. Furthermore, our vaccination regimens generated TH1-biased immune responses in mice. Most importantly, prime-boost vaccination of a Syrian hamster infection model with MVA-S and v-NY-S protected the hamsters against SARS-CoV-2 infection, supporting that these two vaccines are promising candidates for future development. Finally, our vaccination regimens generated neutralizing antibodies that partially cross-neutralized SARS-CoV-2 variants of concern.

immunology↗

bioRxiv2020

SlSWEET15 exports sucrose from phloem and seed coat in tomato to supply carbon for fruit and seed development

Tomato, an important fruit crop worldwide, requires efficient sugar allocation for fruit development. However, molecular mechanisms for sugar import to fruits remain poorly understood. Expression of SWEET (Sugars Will Eventually be Exported Transporters) proteins is closely linked with hexose ratio in tomato fruits and may be involved in sugar allocation. Here, using quantitative PCR, we discovered that SlSWEET15 was highly expressed in developing fruits compared to vegetative organs. Based on in situ hybridization and GUS fusion analyses, SlSWEET15 proteins accumulated in vascular tissues and seed coats, major sites of sucrose unloading in fruits. Localizing SlSWEET15-GFP to the plasma membrane supported its putative role in apoplasmic sucrose unloading. The sucrose transport activity of SlSWEET15 was confirmed by complementary growth assays in a yeast mutant. Elimination of the SlSWEET15 function by CRISPR/cas9 gene editing significantly decreased average sizes and weights of fruits, with severe defects in seed filling and embryo development. Together, we confirmed the role of SlSWEET15 in mediating sucrose efflux from the releasing phloem to the fruit apoplasm and subsequent import into parenchyma cells during fruit development. Furthermore, SlSWEET15-mediated sucrose efflux was also required for sucrose unloading from the seed coat to the developing embryo. One-sentence SummarySlSWEET15, a specific sucrose uniporter in tomato, mediates apoplasmic sucrose unloading from releasing phloem cells and seed coat for carbon supply during fruit expansion and seed filling.

plant biology↗