Abstract
Ultraviolet-B radiation (UV-B: 280-320 nm) has pleiotropic effects on plant development. We have previously demonstrated that alignment of chloroplast in palisade cells become irregular and palisade cells become like spongy cells by UV-B irradiation in cucumber cotyledon. Recently, the Cs1-MMP gene was isolated from a cucumber cotyledon. Cs1-MMP encodes a putative matrix metalloproteinase (MMP) and is expressed at the boundary of senescence and programmed cell death (PCD) of the cotyledon. In animals, MMPs make up a major group of enzymes that degrade the extracellular cell matrix (ECM). To investigate the possibility that UV-B irradiation induces PCD in cucumber cotyledon, Cs1-MMP expression and DNA fragmentation were analyzed. Cs1-MMP expression was induced by UV-B irradiation. However, DNA fragmentation was not detected in cucumber cotyledon irradiated by UV-B for 15 days. Further study is necessary to characterize cell death in cucumber cotyledon irradiated by UV-B.
