Premium
Ge SUT4 mediates sucrose import at the symbiotic interface for carbon allocation of heterotrophic Gastrodia elata (Orchidaceae)
Author(s) -
Ho LiHsuan,
Lee YungI,
Hsieh ShuYing,
Lin IShiuan,
Wu YunChien,
Ko HanYu,
Klemens Patrick A.,
Neuhaus H. Ekkehard,
Chen YiMin,
Huang TzuPi,
Yeh ChihHsin,
Guo WoeiJiun
Publication year - 2021
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/pce.13833
Subject(s) - sucrose , orchidaceae , biology , botany , yeast , sugar , biochemistry , chemistry
Gastrodia elata , a fully mycoheterotrophic orchid without photosynthetic ability, only grows symbiotically with the fungus Armillaria . The mechanism of carbon distribution in this mycoheterotrophy is unknown. We detected high sucrose concentrations in all stages of Gastrodia tubers, suggesting sucrose may be the major sugar transported between fungus and orchid. Thick symplasm‐isolated wall interfaces in colonized and adjacent large cells implied involvement of sucrose importers. Two sucrose transporter (SUT)‐like genes, GeSUT4 and GeSUT3 , were identified that were highly expressed in young Armillaria ‐colonized tubers. Yeast complementation and isotope tracer experiments confirmed that Ge SUT4 functioned as a high‐affinity sucrose‐specific proton‐dependent importer. Plasma‐membrane/tonoplast localization of Ge SUT4‐GFP fusions and high RNA expression of GeSUT4 in symbiotic and large cells indicated that Ge SUT4 likely functions in active sucrose transport for intercellular allocation and intracellular homeostasis. Transgenic Arabidopsis overexpressing GeSUT4 had larger leaves but were sensitive to excess sucrose and roots were colonized with fewer mutualistic Bacillus , supporting the role of Ge SUT4 in regulating sugar allocation. This is not only the first documented carbon import system in a mycoheterotrophic interaction but also highlights the evolutionary importance of sucrose transporters for regulation of carbon flow in all types of plant‐microbe interactions.