The role of CORYMBOSA1/BIG and auxin in the growth of Arabidopsis pedicel and internode.

The developmental regulation of pedicel and internode ensures that plants of the same species have similar inflorescence architecture. In Arabidopsis, the elongation of pedicels and internodes must be temporally and spatially regulated. We previously isolated the corymbosa1 (crm1) mutant, which has a corymb-like inflorescence because of shortened pedicels and internodes. CRM1/BIG encodes a membrane-associated protein and is required for auxin transport. Although CRM1/BIG and auxin have important roles in the development of pedicels and internodes, the developmental changes in cell growth in pedicels and internodes have not been examined. Here, we investigated the role of auxin in the cell growth of pedicels and internodes. Wild-type plants had rapid pedicel and internodal elongation that resulted from the temporal control of cell division and elongation. The crm1 mutants had defects in cell division and elongation. Auxin signaling and cell cycle gene expression in crm1 inflorescences were lower than those in the wild type. Moreover, wild-type plants treated with an auxin transport inhibitor and mutants defective in auxin signaling had shorter pedicels and internodes, with fewer and smaller cells. Our results suggest that auxin transport and signaling have important roles in controlling the proliferation and elongation of pedicel and internodal cells.

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