Overexpression of the Vacuolar Sugar CarrierAtSWEET16Modifies Germination, Growth, and Stress Tolerance in Arabidopsis  

Abstract

Here, we report that SUGARS WILL EVENTUALLY BE EXPORTED TRANSPORTER (SWEET16) from Arabidopsis (Arabidopsis thaliana) is a vacuole-located carrier, transporting glucose (Glc), fructose (Fru), and sucrose (Suc) after heterologous expression in Xenopus laevis oocytes. The SWEET16 gene, similar to the homologs gene SWEET17, is mainly expressed in vascular parenchyma cells. Application of Glc, Fru, or Suc, as well as cold, osmotic stress, or low nitrogen, provoke the down-regulation of SWEET16 messenger RNA accumulation. SWEET16 overexpressors (35S Pro :SWEET16) showed a number of peculiarities related to differences in sugar accumulation, such as less Glc, Fru, and Suc at the end of the night. Under cold stress, 35S Pro :SWEET16 plants are unable to accumulate Fru, while under nitrogen starvation, both Glc and Fru, but not Suc, were less abundant. These changes of individual sugars indicate that the consequences of an increased SWEET16 activity are dependent upon the type of external stimulus. Remarkably, 35S Pro :SWEET16 lines showed improved germination and increased freezing tolerance. The latter observation, in combination with the modified sugar levels, points to a superior function of Glc and Suc for frost tolerance. 35S Pro :SWEET16 plants exhibited increased growth efficiency when cultivated on soil and showed improved nitrogen use efficiency when nitrate was sufficiently available, while under conditions of limiting nitrogen, wild-type biomasses were higher than those of 35S Pro :SWEET16 plants. Our results identify SWEET16 as a vacuolar sugar facilitator, demonstrate the substantial impact of SWEET16 overexpression on various critical plant traits, and imply that SWEET16 activity must be tightly regulated to allow optimal Arabidopsis development under nonfavorable conditions.

UV-C treatment on physiological response of potato (Solanum tuberosum L.) during low temperature storage

“…This may related to the fact that the sugars are effective in the regulation of osmotic pressure in plant cells. Researchers have also shown that over-expression of vacuole sugar transporter AtSWEET16 may modify the process of stress tolerance in Arabidopsis (Klemens et al 2013). Sugar-induced tolerance to the herbicide atrazine in Arabidopsis seedlings has also been shown to be related to the oxidative and xenobiotic stress responses (Sulmon et al 2006).…”

A genome-wide analysis of SWEET gene family in cotton and their expressions under different stresses

“…Many SWEET genes in different plants are the key factors that regulate the redistribution of soluble sugar and respond to many abiotic stresses at the transcriptional level, indicating that they may be closely related to plant stress response (Yuan and Wang 2013;Klemens et al 2013;Seo et al 2011). The mutants have defects of AtSWEET11 and AtSWEET12 affects freezing tolerance in Arabidopsis (Hir et al 2015).…”

“…AtSWEET15 can be induced by cold, salt and drought stress (Seo et al 2011). Overexpressing AtSWEET16 improved the tolerance to cold stress, osmotic stress and nitrogen availability in Arabidopsis (Klemens et al 2013). In addition, SWEETs from other plants (e.g., Hordeum vulgare, tomato, etc.)…”

“…Other SWEETs have the function of transporting fructose and galactose (Klemens et al 2013;Guo et al 2014;Zhou et al 2014). AtSWEET16 and AtSWEET17 are highly expressed in roots and involved in the transport of monosaccharides and polysaccharides across tonoplast (Klemens et al 2013;Guo et al 2014;Chardon et al 2013). In addition, SWEETs participate in the transport of sugar and ions.…”

SWEET17, a Facilitative Transporter, Mediates Fructose Transport across the Tonoplast of Arabidopsis Roots and Leaves

“…Mutations of SWEET8/Ruptured pollen grain1 in Arabidopsis, and RNA inhibition of OsSWEET11 (also called Os8N3 or Xa13) in rice, and petunia (Petunia hybrida) NEC1 resulted in male sterility (Ge et al, 2001;Yang et al, 2006;Guan et al, 2008), possibly caused by inhibiting the Glc supply to developing pollen (Guan et al, 2008). Interestingly, two members, SWEET16 and SWEET17, of the family localize to the tonoplast Klemens et al, 2013). Allelic variation or mutations that affect SWEET17 expression caused Fru accumulation in Arabidopsis leaves, indicating that it plays a key role in exporting Fru from leaf vacuoles .…”