Programmed cell death during flower senescence: isolation and characterization of cysteine proteinases from Sandersonia aurantiaca

Abstract

Cysteine protease inhibitors delayed the senescence of Sandersonia aurantiaca Hook. flowers. Tepal fading and wilting occurred later in the 2,2� -dipyridyl-treated flowers, and these flowers had a greater soluble protein content and less active endoproteases compared with control flowers that were held in water. Biochemical analysis revealed the presence of several protease-active bands in the soluble protein fraction of Sandersonia tepals. Activity of the polypeptides increased as flower senescence progressed. Western analysis with an antibody raised against the castor bean cysteine proteinase identified homologous proteins in Sandersonia flowers (ca 46, 41 and 31�kDa). Three cDNAs encoding cysteine proteinases were isolated from Sandersonia tepals (PRT5, PRT15 and PRT22). Expression of all three increased in tepals as senescence progressed. mRNAs for PRT5 were detected only in senescing flower tissue, whereas PRT15 and PRT22 were expressed in leaf, stem and root tissue. PRT5 has significant homology to C-terminus KDEL proteins, which have a role in the degradation of plant cell contents during programmed cell death. PRT15 is most similar to cysteine proteinases with a long C-terminal extension, whereas PRT22 is homologous to stress-induced cysteine proteinases.

Physiological and biochemical changes associated with flower development and senescence in Consolida ajacis Nieuwl cv. Violet blue

“…The decrease in protein content was commensurate with the increase in specific protease activity and to the tissue content of α-amino acids, which supports the earlier findings on other flower systems (Lay-Yee et al, 1992;Wagstaff et al, 2002;Jones et al, 2005;Lerslerwong et al, 2009;Tripathi et al, 2009). The degradation of proteins by proteolytic cleavage and the remobilization of degradation products (amino acids) to the developing tissues are thought to play a significant role in the senescence of flowers, as the expression of protease genes is one of the earliest senescencerelated gene changes to be identified, and the free amino acids are transported via phloem to other tissues of the same flower as the developing pistil (Solomon et al, 1999;Eason et al, 2002). Beers et al (2000) reported endopeptidases to be one of the most well-characterized cell death proteins in plants particularly those of cysteine proteases.…”

“…Beers et al (2000) reported endopeptidases to be one of the most well-characterized cell death proteins in plants particularly those of cysteine proteases. These proteases have been identified and isolated for senescing ethylene-sensitive flowers such as carnations, Petunia and rose (Jones et al, 1995;Jones et al, 2005;Tripathi et al, 2009) as well as ethylene-insensitive flowers as Alstroemeria, Hemerocallis, Sandersonia and gladiolus (Guerrero et al, 1998;Eason et al, 2002;Wagstaff et al, 2002;Arora and Singh, 2004). In some wilting flower systems such as Ipomoea and Petunia, large protein losses as much as 3-8 folds were found to occur prior to senescence, but in C. ajacis, the protein content declined by about 1.8 fold prior to abscission supporting the hypothesis that protein loss occurs least in species showing petal/sepal abscission rather than wilting (Wagstaff et al, 2002).…”

Collection of expressed genes from the transition zone of Cryptomeria japonica in the dormant season

“…We found an EST predicted to encode a papain-type cysteine protease. The predicted protease showed significant sequence similarity to those isolated from the leaves and petals undergoing PCD during senescence [64][65][66][67], suggesting that the protease may be involved in PCD in the TZ as heartwood formation is thought to be a senescence process. The expression level of the corresponding gene for the protease in the TZ was about 5 times higher in June than that in November (Fig.…”

Proteinase inhibitors and their function in plants: A review

“…These processes are associated with activation, in aging tissues of leaves [269][270][271] and flowers [272][273][274], of genes encoding cysteine and serine proteinases. Proteinase inhibitors may also participate in these processes.…”