Heterologous overexpression of strawberry bZIP11 induces sugar accumulation and inhibits plant growth of tomato

Consumers and breeders value strawberry fruit with high sugar content and sweetness. However, many factors negatively affect this trait. bZIP-S1 subfamily was closely correlated with the carbohydrate metabolism. Moreover, it can regulate plant development and growth, and respond to various stress. In the present study, a total of four bZIP-S1 members were identified in strawberry. Quantitative RT-PCR analysis showed a member of this subfamily, designated as bZIP11, most highly expressed in different tissues of strawberry. Especially, it had a significant transcript accumulation during the fruit development and ripening. Constitutive expression of FvbZIP11 in tomato caused severe plant growth retardation which was accompanied by wrinkled and curly leaves. The leaf yellowish and chlorotic patches were reflected in decrease of chlorophyll. Meanwhile, epidermal cells were smaller in leaves of transgenic plant. In addition, the total soluble solid and soluble sugar content of the fruit was significantly higher than WT during the fruit ripening. Taken together, the heterologous overexpression of strawberry bZIP11 induced sugar accumulation and hindered plant growth in tomato, which provided more information for improving strawberry fruit quality.