Vacuolar sugar transporter EARLY RESPONSE TO DEHYDRATION6-LIKE4 affects fructose signaling and plant growth

Abstract

Regulation of intracellular sugar homeostasis is maintained by regulation of activities of sugar import and export proteins residing at the tonoplast. We show here that the EARLY RESPONSE TO DEHYDRATION6-LIKE4 (ERDL4) protein, a member of the monosaccharide transporter family, resides in the vacuolar membrane in Arabidopsis (Arabidopsis thaliana). Gene expression and subcellular fractionation studies indicated that ERDL4 participates in fructose allocation across the tonoplast. Overexpression of ERDL4 increased total sugar levels in leaves due to a concomitantly induced stimulation of TONOPLAST SUGAR TRANSPORTER 2 (TST2) expression, coding for the major vacuolar sugar loader. This conclusion is supported by the finding that tst1-2 knockout lines overexpressing ERDL4 lack increased cellular sugar levels. ERDL4 activity contributing to the coordination of cellular sugar homeostasis is also indicated by two further observations. Firstly, ERDL4 and TST genes exhibit an opposite regulation during a diurnal rhythm, and secondly, the ERDL4 gene is markedly expressed during cold acclimation, representing a situation in which TST activity needs to be upregulated. Moreover, ERDL4-overexpressing plants show larger rosettes and roots, a delayed flowering time, and increased total seed yield. Consistently, erdl4 knockout plants show impaired cold acclimation and freezing tolerance along with reduced plant biomass. In summary, we show that modification of cytosolic fructose levels influences plant organ development and stress tolerance.

Changes in SWEET-mediated sugar partitioning affect photosynthesis performance and plant response to drought

“…It has been proposed for a long time that an excess sugars can trigger negative feedback regulation of leaf photosynthesis (Paul and Foyer 2001; Ainsworth and Bush 2011). In agreement with this, the disruption or overexpression of genes coding for sugar transporters, which potentially impact the cytosolic sugar availability, induce modifications of the photosynthetic performance (Wingenter et al 2010; Frost et al 2012; Khan et al 2023; Liu et al 2023b; Valifard et al 2023). In an effort to gain more knowledge on the physiological consequences of impaired SWEET-mediated sugar transport, we measured chlorophyll fluorescence on the swt11swt12 , swt16swt17 and swt-q mutant lines along with the Col-0 wild-type (WT) plants.…”

“…Briefly, the raw data were transformed using squareroot and a differential expression analysis was performed using the lmfit model of the limma package (Ritchie et al 2015). The Rflomics package was also used to re-analyze the RNA-seq results obtained in Khan et al (2023). Filtering and normalization strategies were performed as described in Lambert et al (2020).…”

Symplasmic phloem loading and subcellular transport in storage roots are key factors for carbon allocation in cassava

“…Conversely, transcripts of proteins involved in vacuolar export such as the H + /sucrose symporter MeSUT4b (Schneider et al, 2012), as well as all three EARLY RESPONSE TO DEHYDRATION 6 ( MeERD6 ) proteins (Kiyosue et al, 1998), and two out of three MeEDL4/ERDL6 orthologs (Poschet et al, 2011) decreased throughout bulking (cluster SR 2 or 3). ERD6 and ERD6-like proteins are part of the MST family and facilitate H + /hexose symport across the tonoplast (Pommerrenig et al, 2018, Khan et al, 2023).…”

“…The MST gene family includes a plethora of genes encoding for proteins involved in tonoplast or plastid transport (Pommerrenig et al, 2018). While transcripts of proteins involved in vacuolar/plastidic import generally increased when cytosolic sugar levels are high, those involved in vacuolar/plastidic export generally decreased in expression under latter conditions (Wormit et al, 2006, Patzke et al, 2018, Klemens et al, 2013, Khan et al, 2023).…”

Be sweet, be strong, and be tolerant: ERDL4 regulates sugar transport and promotes cold tolerance in Arabidopsis

“…In this issue, Khan et al (2023) reported the positive role of ERDL4 ( EARLY RESPONSE TO DEHYDRATION 6-LIKE4 ) in promoting growth and cold tolerance in Arabidopsis. ERDL4 encodes a fructose transporter located at the vacuolar membrane.…”