Analysis of the bamboo SWEET gene family reveals that Dendrocalamus farinosus SWEET14 is involved in source-sink carbohydrate partitioning

In higher plants, SWEET genes play a crucial role in source-sink carbohydrate partitioning. Dendrocalamus farinosus is an economic bamboo species because of its high fiber content and rapid growth. The transportation of photosynthetic products is essential for bamboo growth. Here, we identified 50 major SWEET genes in D. farinosus. Phylogenetic analysis indicated that DfSWEET14 and DfSWEET44 were homologs of OsSWEET11 and OsSWEET4, respectively. DfSWEET5, DfSWEET14 and DfSWEET44 were highly expressed in leaf veins, stems and roots, respectively, and their expression was responsive to glucose and sucrose. DfSWEET9 and DfSWEET28 were involved in photosynthetic product distribution, ABA/MeJA signaling and pathogen responses. DfSWEET14 was localized to the plasma membrane, and was highly expressed in lateral buds and young shoots only. The overexpression of DfSWEET14 in wheat resulted in higher root/shoot biomass ratio under drought stress and increases in grain-filling duration, seed yield, net photosynthetic capacity, soluble sugar content, seed size and grain weight. This suggests that DfSWEET14 is involved in sucrose partitioning from leaves to grains. These results provide new insights into genetic improvement of bamboo and into the breeding of other economic crops for high yield by manipulation of source-sink carbohydrate partitioning and drought responses.