Roles of cell-wall invertases and monosaccharide transporters in the growth and development of Arabidopsis

Abstract

The hydrolysis of sucrose by cell-wall invertases (cwINV) and the subsequent import of hexoses into target cells appears to be crucial for appropriate metabolism, growth and differentiation in plants. Hexose uptake from the apoplast is catalysed by monosaccharide/H+ symporters (Sugar Transport Proteins or STPs), which have the potential to sense sugars. Import of extracellular hexoses may generate signals to orchestrate cellular activities, or simply feed metabolic pathways distinct from those fed by sucrose. It is predicted that Arabidopsis has six cwINV genes and at least 14 STP genes. These genes show different spatial and temporal patterns of expression, and several knock-out mutants have been isolated for analysis. AtSTP1 transports glucose, galactose, xylose, and mannose, but not fructose. It accounts for the majority of the AtSTP activity in vegetative tissues and its activity is markedly repressed by treatment with exogenous sugars. These observations are consistent with a role in the retrieval of cell-wall-derived sugars, for example, during carbohydrate limitation or cell expansion. The AtSTP1 gene is also expressed in developing seeds, where it might be responsible for the uptake of glucose derived from imported sucrose. The large number of AtcwINV and AtSTP genes, together with complex patterns of expression for each, and the possibility that each protein may have more than one physiological function, provides the plant with the potential for a multiplicity of patterns of monosaccharide utilization to direct growth and differentiation or to respond flexibly to changing environmental conditions.

RNA Interference-Mediated Repression of Cell Wall Invertase Impairs Defense in Source Leaves of Tobacco

“…Fully sequenced genomes indicate nine putative cwINVs from rice (Oryza sativa; Ji et al, 2005) and six from Arabidopsis (Arabidopsis thaliana; Sherson et al, 2003), though recent results suggest that Arabidopsis AtcwINV3 and AtcwINV6 are fructan exohydrolases rather than invertases (De Coninck et al, 2005). Similar cwINV families are also reported for poplar (Populus spp.…”

Transcriptome Profiling of Tiller Buds Provides New Insights into PhyB Regulation of Tillering and Indeterminate Growth in Sorghum

“…Increased expression of two genes (Sb0067s002110.1 and Sb0067s002130.1) encoding cell wall invertases (cwINV) in buds of wild-type between 6 DAP and 7 DAP could cleave Suc unloaded into the apoplast to Glc and Fru for uptake by developing buds ( Fig. 6; Sherson et al, 2003;Weschke et al, 2003). A gene encoding an RNase T2 protein expressed at low levels in both phyB-1 and wild-type buds at 6 DAP, was upregulated greater than 10-fold in growing buds of wild-type at 7 DAP and 8 DAP (Supplemental Table S2).…”

“…MtN3 encodes a SWEET transporter, a member of a family of Suc/sugar transporters that are involved in phloem sugar loading/unloading and efflux of sugars from maternal tissues for seed filling and pollen development (Chen et al, 2012;Guo et al, 2014;Chen et al, 2015). CwINVs cleave apoplastic Suc into Glc and Fru for import into cells (Sherson et al, 2003;Weschke et al, 2003). Increased expression of the SWEET transporter in the phloem could facilitate unloading of Suc into the apoplast where cwINVs generate Glc and Fru for uptake by developing buds.…”

Sugar metabolism ofVetiveria zizanioidescells cultured with Amberlite XAD-4. Uptake of radiolabelled sugars, cell wall invertase activity and gene expression

“…Differential affinity for glucose and fructose has been reported for many plant cell cultures (Sherson et al 2003;Kretzschmar et al 2007 and references therein). These monosaccharides represent the principal source of carbon and energy in most cells, and a significantly higher affinity of the membrane transporters for glucose is almost the rule.…”

“…Depending on the species and cell type, hexoses released into the culture media are then taken up by passive or active processes, through hexose-specific transporters (Stepan-Sarkissian and Fowler 1986;Roitsch et al 2003;Kato et al 2007). Once inside, hexoses have a great capacity to stimulate specific sugar sensors (Koch 2004 and references therein) and the resulting signals can alter expression of diverse genes (Smeekens 2000;Rolland et al 2002;Sherson et al 2003). With their hydrolytic activity, therefore, invertases are potentially strong effectors of widely varying developmental processes LeClere et al 2008), including the biosynthesis and perception of auxins and abscisic acid (Koch 2004 and references therein; Arru et al 2008).…”