The homo/heterodimers of plasma membrane sugar transporters CsSWEET1a
and CsSWEET17 mediate growth and cold stress tolerance
Abstract
Sugars will eventually be exported transporters (SWEET) are involved in
plant biological processes. CsSWEET1a and CsSWEET17, were found to be
induced by cold acclimation in Camellia sinensis. Particularly,
CsSWEET17 was differentially alternatively spliced and its
inclusion/exclusion ratio was higher in the cold-resistant cultivar than
in the cold-susceptible cultivars. Both CsSWEET1a and CsSWEET17 were
located in the plasma membrane, and their interaction was confirmed
using yeast two-hybrid and biomolecular fluorescence complementation.
The C-terminal of the CsSWEET17, which was different from AtSWEET17, did
not affect its plasma membrane localization but promoted its sugar
transport activities. Overexpression (OE) of CsSWEET1a and CsSWEET17
resulted in an increased uptake of sugars in Arabidopsis, affecting
plant germination and growth. The leaf and seed size of CsSWEET17-OE
lines were significantly bigger than wild-type. Moreover, OE of
CsSWEET1a and CsSWEET17 significantly reduced the relative electrolyte
leakage levels under cold stress. Compared with those in wild-type, the
expressions of AtCWINV genes were suppressed in both CsSWEET1a-OE and
CsSWEET17-OE lines, indicating the alteration of sugar contents in the
cell wall of OE lines. Our results suggest that CsSWEET1a and CsSWEET17
form homo/heterodimers in the plasma membrane to import sugars into the
cytoplasm, thereby regulating plant growth and cold tolerance.