Heterologous expression of bacterial trehalose biosynthetic genes enhances trehalose accumulation in potato plants without adverse growth effects

Trehalose is a non-reducing disaccharide found in various organisms, including bacteria, fungi, invertebrates, and plants. It plays essential roles in diverse biological processes such as stress resistance, metabolism, and development in plants. Despite the important role of trehalose, it is challenging to increase trehalose levels because of its negative effects on plant growth and development. In this study, we tested several combinations of different promoters and trehalose biosynthetic genes to efficiently accumulate trehalose in potato plants. Transgenic potato plants expressing TPSP (trehalose-6-phosphate synthase/phosphatase) fusion gene under the control of Rd29A promoter increased trehalose content in response to high salt stress and did not show significant growth retardation. Although constitutive overexpression of plastid-targeted MTSH (maltooligosyltrehalose synthase/trehalohydrolase) fusion gene driven by CaMV 35S promoter remarkably accumulated trehalose, the transgenic potato plants showed a severely stunted phenotype. By contrast, stress-inducible expression of plastid-targeted MTSH under the control of Rd29A promoter led to trehalose accumulation without growth defects in response to high salt stress. Besides, tuber-specific expression of plastid-targeted MTSH driven by GBSS (granule-bound starch synthase) promoter specifically increased trehalose level in potato tubers without stunting growth. Consequently, we suggest that heterologous expression of TPSP and MTSH fusion genes driven by stress-inducible or tuber-specific promoters can be an effective strategy for accumulating trehalose in potato plants as well as minimizing its adverse effects on potato growth.