PT  - JOURNAL ARTICLE
AU  - Jiang Wang
AU  - Ya-Chi Yu
AU  - Ye Li
AU  - Li-Qing Chen
TI  - The hexose transporter SWEET5 confers galactose sensitivity to Arabidopsis pollen germination via the galactokinase GALK
AID  - 10.1101/2021.04.07.438853
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.04.07.438853
4099  - http://biorxiv.org/content/early/2021/09/15/2021.04.07.438853.short
4100  - http://biorxiv.org/content/early/2021/09/15/2021.04.07.438853.full
AB  - Galactose is an abundant and essential sugar used for the biosynthesis of many macromolecules in different organisms, including plants. Galactose metabolism is tightly and finely controlled since excess galactose and derivatives are inhibitory. In Arabidopsis, root growth and pollen germination were strongly inhibited by excess galactose. However, the mechanism of galactose induced inhibition during pollen germination remains obscure. In this study, we characterized a plasma-membrane localized transporter, AtSWEET5, that transports glucose and galactose. SWEET5 protein level started to accumulate at the tricellular stage of pollen development and peaked in mature pollen before rapidly declining after pollen was germinated. SWEET5 levels are responsible for the dosage-dependent sensitivity of galactose and galactokinase (GALK) is essential for the inhibitory effects of galactose during pollen germination. Overall, SWEET5 and GALK contribute to the maintenance of galactose metabolic homeostasis during pollen germination. SWEET5 serves as a major low-affinity hexose transporter at the early stage of pollen germination.One-sentence summary SWEET5 mediates pollen galactose sensitivity via GALK that is required for efficient galactose uptake in pollen during pollen germination.Competing Interest StatementThe authors have declared no competing interest.