Functional differences in transport properties of natural HKT 1;1 variants influence shoot Na + exclusion in grapevine rootstocks

• Published in: The New phytologist Vol. 217; no. 3; pp. 1113 - 1127
• Main Authors: Henderson, Sam W., Dunlevy, Jake D., Wu, Yue, Blackmore, Deidre H., Walker, Rob R., Edwards, Everard J., Gilliham, Matthew, Walker, Amanda R.
• Format: Journal Article
• Language: English
• Published: 01-02-2018
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.14888

Under salinity,
Vitis
spp. rootstocks can mediate salt (NaCl) exclusion from grafted
V. vinifera
scions enabling higher grapevine yields and production of superior wines with lower salt content. Until now, the genetic and mechanistic elements controlling sodium (Na
+
) exclusion in grapevine were unknown.
Using a cross between two
Vitis
interspecific hybrid rootstocks, we mapped a dominant quantitative trait locus (
QTL
) associated with leaf Na
+
exclusion (
NaE
) under salinity stress. The
NaE
locus encodes six high‐affinity potassium transporters (
HKT
). Transcript profiling and functional characterization in heterologous systems identified
Vis
HKT
1;1
as the best candidate gene for controlling leaf Na
+
exclusion.
We characterized four proteins encoded by unique
Vis
HKT
1;1
alleles from the parents, and revealed that the dominant
HKT
variants exhibit greater Na
+
conductance with less rectification than the recessive variants. Mutagenesis of Vis
HKT
1;1 and Ta
HKT
1.5‐D from bread wheat, demonstrated that charged amino acid residues in the eighth predicted transmembrane domain of
HKT
proteins reduces inward Na
+
conductance, and causes inward rectification of Na
+
transport.
The origin of the recessive
Vis
HKT
1;1
alleles was traced to
V. champinii
and
V. rupestris
. We propose that the genetic and functional data presented here will assist with breeding Na
+
‐tolerant grapevine rootstocks.