Transcriptome analysis of colchicine-induced tetraploid Kiwifruit leaves with increased biomass and cell size

Colchicine-induced polyploidization has been extensively utilized in plant-breeding programs to increase biomass and overall yield of various crop species. Chromosome doubling usually increases the plant size and cell size. However, the underlying mechanisms remain elusive. In this study, we showed that 0.1% colchicine is an optimized concentration for inducing tetraploidization of Actinidia chinensis var. chinensis 'Hongyang', a commercially important diploid kiwifruit cultivar. The tetraploid plants showed increased plant height, leaf size, and biomass, as compared with the corresponding diploid plants. Scanning electron microscopy and histological analysis indicated that the leaf cell size was significantly increased in the tetraploid plants. Our further transcriptome analysis revealed the 5922 differentially expressed genes between the diploid and tetraploid plants. Gene Ontology analysis enriched the cell wall-related genes, including the pectin methylesterases (PMEs) and expansins (EXPs), both of which play a critical role in cell wall loosening and extension. The increased expression of PME and EXP genes might contribute to the increased cell size in the tetraploid plants. Together, our work indicated that tetraploidization increases the organ and cell size in kiwifruit, possibly by enhancing the cell wall extensibility.