Temporal and spatial expression of a thiolprotease gene during pea ovary senescence, and its regulation by gibberellin

Abstract

Clones encoding a thiolprotease (tpp) have been isolated from a cDNA library of unpollinated, senescent pea ovaries and its pattern of expression during both ovary senescence and parthenocarpic development have been studied. The sequence of the tpp cDNA displays a high similarity with other plant and animal thiolproteases of the papain group. The homology is highest around the Cys-His of the active centre; a 109 amino acid sequence at the carboxy terminus was found to be homologous only to thiolproteases of plant origin; this part of the mRNA is also present in another pea mRNA that exhibits similar patterns of induction. tpp mRNA shows a temporal pattern of accumulation that precedes that observed for proteolytic activity. Such accumulation did not occur when ovaries were induced to grow parthenocarpically by gibberellic acid (GA) treatment; furthermore the initial low level of expression present in ovaries decreased after GA treatment, indicating that the gene is down-regulated by gibberellins. Spatially, tpp mRNA is localized mainly within the ovule and ovary vascular elements, and transiently within the endocarp of senescent ovaries. This pattern of expression precedes the development of the cytopathogenic effects observed as unpollinated ovaries undergo senescence.

Gibberellins Inhibit Nodule Senescence and Stimulate Nodule Meristem Bifurcation in Pea (Pisum sativum L.)

“…In addition, the transcript abundance of all analyzed genes was significantly higher in the nodules of untreated plants than in nodules of plants treated with GA 3 at 6 WAI, which may indicate a delay of nodule senescence upon treatment with exogenous GA 3 (Figure 10C). It is known that cysteine proteases carry out large-scale protein degradation during nodule senescence (Pladys et al, 1991; Granell et al, 1992; Kardailsky and Brewin, 1996; Van de Velde et al, 2006; Pérez Guerra et al, 2010). Thus, our data suggest that a decrease in GAs is required to induce the degradation processes during nodule aging.…”

Ethylene is involved in pistil fate by modulating the onset of ovule senescence and the GA-mediated fruit set in Arabidopsis

“…Unpollinated pea pistil senescence involves programmed cell death, which initiates at 2-3 days post-anthesis (DPA) [1,5,6]. Its onset correlates with both the expression of proteolytic activities [7-9] and the whole pistil's cell degradation [2], including DNA fragmentation in specific cells at both the ovary wall and ovules [6]. More recently, we showed that the development of the Arabidopsis unfertilised pistil differs from that of pea since the Arabidopsis ovary wall shows developmental characteristics that are shared with a developing fruit, while senescence is specifically established first at the stigma, and then progresses from basal to apical ovules [4].…”