Sucrose Transporter AtSUC9 Mediated by a Low Sucrose Level is Involved in Arabidopsis Abiotic Stress Resistance by Regulating Sucrose Distribution and ABA Accumulation

Abstract

Sucrose (Suc) transporters (SUCs or SUTs) are important regulators in plant growth and stress tolerance. However, the mechanism of SUCs in plant abiotic stress resistance remains to be dietermined. Here, we found that AtSUC9 expression was induced by abiotic stress, including salt, osmotic and cold stress conditions. Disruption of AtSUC9 led to sensitive responses to abiotic stress during seed germination and seedling growth. Further analyses indicated that the sensitivity phenotype of Atsuc9 mutants resulted from higher Suc content in shoots and lower Suc content in roots, as compared with that in wild-type (WT) plants. In addition, we found that the expression of AtSUC9 is induced in particular by low levels of exogenous and endogenous Suc, and deletion of AtSUC9 affected the expression of the low Suc level-responsive genes. AtSUC9 also showed an obvious response to treatments with low concentrations of exogenous Suc during seed germination, seedling growth and Suc distribution, and Atsuc9 mutants hardly grew in abiotic stress treatments without exogenous Suc. Moreover, our results illustrated not only that deletion of AtSUC9 blocks abiotic stress-inducible ABA accumulation but also that Atsuc9 mutants had a lower content of endogenous ABA in stress conditions than in normal conditions. Deletion of AtSUC9 also inhibited the expression of many ABA-inducible genes (SnRk2.2/3/6, ABF2/3/4, ABI1/3/4, RD29A, KIN1 and KIN2). These results indicate that AtSUC9 is induced in particular by low Suc levels then mediates the balance of Suc distribution and promotes ABA accumulation to enhance Arabidopsis abiotic stress resistance.

Overexpression of a Grapevine Sucrose Transporter (VvSUC27) in Tobacco Improves Plant Growth Rate in the Presence of Sucrose In vitro

“…Thus, NtSUT1 is essential for sucrose export, even when sugar biosynthesis was reduced or soluble sugars accumulated (Burkle et al, 1998). In this study, we compared the expression level of NtSUT1 in medium with and without sucrose and found that NtSUT1 was highly upregulated in the presence of low levels of exogenous sucrose (Figure 10B), which was consistent with the findings for AtSUC9 in Arabidopsis (Jia et al, 2015). When grown in the no-sucrose medium, the expression of NtSUT1 in the transformants was slightly reduced in the roots; however, it was increased in the stems and leaves (Figure 10B).…”

“…Thus far, results on the role of sucrose transporters at the whole-plant level under abiotic stress conditions have revealed a sucrose imbalance in the sink and source, and hypersensitivity in response to abiotic stress treatments when they were induced by defective SUT function, including AtSUC2, AtSUC4, AtSUC9, and PtaSUT4 (Frost et al, 2012; Gong et al, 2015; Jia et al, 2015). This suggests that sucrose transporters might be involved in the redistribution of sucrose, which is useful for plants to resist abiotic stress.…”

Regulation of Sucrose Transporters and Phloem Loading in Response to Environmental Cues

“…The downregulation of AtSUC1 could mean that Suc partitioning is stopped under various stress conditions, including water, salt, heat, and light stress. That AtSUC9, which has also been linked to abiotic stress resistance (Jia et al, 2015), does not show changes here is not surprising considering that its domain of action does not include leaves.…”

“…There is increasing evidence that different types of SUTs are involved in the response to abiotic stress (Sivitz et al, 2008;Frost et al, 2012;Gong et al, 2015;Jia et al, 2015). Based on the extensive transcriptomics data available for drought, salt, and heat stress, these data are extended here by the identification of patterns in the response of SUT expression.…”

Sucrose Transporter ZmSut1 Expression and Localization Uncover New Insights into Sucrose Phloem Loading

“…In the coming decades, a growing world population (predicted to increase by more than 2 billion people by 2050) will place increasing pressure on agricultural systems already challenged with the increased temperatures and more erratic precipitation patterns predicted for climate change (Godfray et al, 2010;Rosenzweig et al, 2014). Hence, understanding the transport pathways and genes functioning to control the allocation of carbohydrates in plants will be crucial to improve crop resilience to biotic and abiotic stress and to increase crop productivity (Rennie and Turgeon, 2009;Bihmidine et al, 2013;Lemoine et al, 2013;Braun et al, 2014;Jia et al, 2015;Yadav et al, 2015;Durand et al, 2016).…”