Characterization of the cysteine protease, PhCP10, during the senescence of Petunia x hybrida flowers
Proteases play an important role in the degradation and remobilization of proteins during flower senescence. The majority of proteases that are upregulated during senescence and programmed cell death are from the cysteine protease class of proteases. Recently, nine putative cysteine proteases were identified from Petunia x hybrida. Six of the nine cysteine proteases were upregulated during petal senescence. One cysteine protease, PhCP10, is upregulated early in senescence, is expressed only in senescing tissues and appears to be regulated by ethylene. The PhCP10 sequence shows high homology to SAG12 (senescence-associated gene) from Arabidopsis. SAG12 is senescence specific in Arabidopsis leaves, but little is known about its expression in flowers. TAIL-PCR was preformed to obtain the PhCP10 promoter . The PhCP10 promoter sequence also shares homology with the senescence-specific and basal promoter regions of SAG12. Promoter constructs driving GFP expression have been analyzed utilizing transient expression in lima bean cotyledons and in petunia flowers. Transient expression in lima beans and petunia flowers has detected a possible regulatory element that appears to enhance PhCP10 expression in a similar manner to the enhancer region in the SAG12 promoter. We are currently transforming petunias with the PhCP10:GFP constructs to further characterize the temporal and spatial expression of PhCP10 during flower senescence and following ethylene treatment.
Flower senescence, cysteine protease