At2-MMP Is Required for Attenuation of Cell Proliferation during Wound Healing in Incised Arabidopsis Inflorescence Stems

Wound healing of partially incised Arabidopsis inflorescence stems constitutes cell proliferation that initiates mainly in pith tissues about 3 d after incision and the healing process that completes in about 7 d. Although the initiation mechanisms of cell proliferation have been well documented, the suppression mechanisms remain elusive. Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases well known as proteolytic enzymes in animal system functioning in extracellular matrix remodeling during physiological and pathological processes, including tissue differentiation, growth, defense, wound healing and control of cancer growth. In this study, we report that At2-MMP might contribute to the suppression mechanism for cell proliferation during the tissue-repair process of incised inflorescence stems. At2-MMP transcript was gradually upregulated from day 0 to 5 after incision and slightly decreased on day 7. Morphological analysis of incised stem of defected mutant at2-mmp revealed significantly enhanced cell proliferation around the incision site. Consistent with this, semi-quantitative analysis of dividing cells displayed a significant increment in the number of dividing cells in at2-mmp as compared to wild type. These results showed that the upregulation of At2-MMP at a later stage of the wound-healing process is likely to be involved in the completion of the process by attenuating cell proliferation.