Wounding Enhances Expression of AtSUC3, a Sucrose Transporter from Arabidopsis Sieve Elements and Sink Tissues

Abstract

The Arabidopsis AtSUC3 gene encodes a sucrose (Suc) transporter that differs in size and intron number from all other Arabidopsis Suc transport proteins. Each plant species analyzed so far possesses one transporter of this special type, and several functions have been discussed for these proteins, including the catalysis of transmembrane Suc transport, and also Suc sensing and regulation of other Suc transporters. Here, we show that the AtSUC3 protein is localized in the sieve elements of the Arabidopsis phloem and is not colocalized with the companion cell-specific AtSUC2 phloem loader. Even stronger AtSUC3 expression is observed in numerous sink cells and tissues, such as guard cells, trichomes, germinating pollen, root tips, the developing seed coat, or stipules. Moreover, AtSUC3 expression is strongly induced upon wounding of Arabidopsis tissue. The physiological role of AtSUC3 in these different cells and tissues is discussed.

A Plasma Membrane-Anchored Fluorescent Protein Fusion Illuminates Sieve Element Plasma Membranes in Arabidopsis and Tobacco

“…Whereas no such domain has been reported previously in the literature, the promoter of a related Suc-H 1 symporter, AtSUC3p, driving the expression of a membrane protein-GFP fusion, was shown to express strongly in the root tip epidermis (Meyer et al, 2004). The failure to observe a root tip epidermal expression domain in earlier work with AtSUC2p could be due the fact that a shorter, 900-bp fragment of the promoter was employed (a 900-bp fragment from plasmid pEPS1; Stadler et al, 2005), in contrast to the 2,141-bp fragment used here.…”

Genetic Control of Carbon Partitioning in Grasses: Roles of Sucrose Transporters and Tie-dyed Loci in Phloem Loading

“…However, subsequent studies have questioned this hypothesis by finding that null mutations in AtSUC3 have no obvious phenotype and that AtSUC3 protein has measurable biochemical activity (Meyer et al, 2000;Barth et al, 2003). Interestingly, the gene is expressed in many sink tissues and is strongly induced by wounding (Meyer et al, 2000(Meyer et al, , 2004. The only report characterizing a group 3 SUT in grasses showed that the rice OsSUT4 gene is expressed in all tissues examined, although at higher levels in sink leaves (Aoki et al, 2003).…”

Differential vascularization of nematode-induced feeding sites

“…The direction of assimilate flow from the apoplast is dependent on the chemical gradient, which, because of the high sink strength, is directed toward GCs. Additionally, because of the lack of CCs, the sucrose transporters AtSUC2 and AtSUC3, which have been postulated to retrieve sucrose that is lost from the phloem along the transport pathway, are absent from RKs (37,38). Consequently, nSEs lack the ability to retrieve sucrose.…”