Overexpression of Arabidopsis cyclin D2;1 in cotton results in leaf curling and other plant architectural modifications

The D-class cyclin genes play key roles in controlling the cell cycle in plant development. To evaluate the effects of D-type cyclins on plant architecture, ectopic expression of the Arabidopsis cyclinD2;1 (Arath;CYCD2;1) gene driven by the CaMV35S promoter was investigated in cotton via Agrobacterium-mediated transformation. Northern blot showed the cyclinD2;1 gene was highly expressed in transgenic cotton plants. Phenotype investigation showed that overexpression of Arath;CYCD2;1 led to obvious leaf architecture change: the leaf epidermis of transgenic plants consist of more small cells compared to the wild-type. Mesophyll cells in the inner layers of Arath;CYCD2;1 plants were organized more loosely than those in the inner layers of wild-type plants. Moreover, transgenic plants had darker leaves, more chlorophyll, and a higher rate of photosynthesis than wild-type plants in the field. Tissue cultures indicated that the overexpression of Arath;CYCD2;1 promoted callus formation in the absence of exogenous auxin, but inhibited cell differentiation. The qRT-PCR revealed that several cell cycle-associated genes, particularly the transcript levels of GhRBR and GhCYCD3;1 were regulated by the Arath; CYCD2;1 insertion. The results implied that the cotton plant architecture or cell culture characters could be regulated by ectopic expression of the Arabidopsis cyclinD2;1 gene.