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Abstract

The often rapid and synchronous programmed death of petal cells provides a model system to study molecular aspects of organ senescence. The death of petal cells is preceded by a loss of membrane permeability, due in part to increases in reactive oxygen species that are in turn related to up-regulation of oxidative enzymes and to a decrease in activity of certain protective enzymes. The senescence process also consists of a loss of proteins caused by activation of various proteinases, a loss of nucleic acids as nucleases are activated, and enzyme-mediated alterations of carbohydrate polymers. Many of the genes for these senescence-associated enzymes have been cloned. In some flowers, the degradative changes of petal cells are initiated by ethylene; in others, abscisic acid may play a role. External factors such as pollination, drought and temperature stress also affect senescence, perhaps by interacting with hormones normally produced by the flowers. Signal transduction may involve G-proteins, calcium activity changes and the regulation of protein phosphorylation and dephosphorylation. The efficacy of the floral system as well as the research tools now available make it likely that important information will soon be added to our knowledge of the molecular mechanisms involved in petal cell death.

AtGAT1, a High Affinity Transporter for γ-Aminobutyric Acid in Arabidopsis thaliana

“…The higher AtGAT1 transcript levels in sepals and petals correlate with increased expression of other senescence-associated genes, e.g. pheophorpide a oxygenase, which again points to a role of AtGAT1 during senescence (61,62). The role of GABA during senescence is not clear, but Bouché and Fromm (13) speculated that GABA might act as a signaling molecule to coordinate carbon:nitrogen balance in changing nutrient environments, as it occurs during senescence (49).…”

Senescence and programmed cell death in plants: polyamine action mediated by transglutaminase

“…At the subcellular level, mitochondria may play a central role, retaining their function during senescence, since respiration continues by alternative oxidase (Vanlerberghe, 2013). Increase of ROS production and protease and nuclease activities have been reported during the leaf senescence (Quirino et al, 2000; Rubinstein, 2000). The cross-talk of nitric oxide and reactive oxygen species in plant PCD (Wang et al, 2013) as well as catabolic and interconversion products of PAs (Moschou and Roubelakis-Angelakis, 2013) have been recently reviewed.…”

“…The fact that the antibody raised against Arabidopsis TGase recognizes some proteins of Nicotiana , also immunodetected by two animal antibodies, and that plant and animal TGases present similar molecular weights and modify GFP in a similar way, would suggest a similarity among these enzymes. However, plant and animal PCD are dissimilar due to the cell structure; in fact, typical plant organelles, such as chloroplasts, vacuoles, and also possibly the cell walls, play a role in the induction or execution of PCD, as reported during the leaf and petal senescence (Quirino et al, 2000; Rubinstein, 2000; Lim et al, 2007). The localization of TGase in the Nicotiana petal cells could suggest new and different roles of this enzyme in PCD in addition to those detected in animal cells.…”

Influence of Citric Acid and Hydrogen Peroxide on Postharvest Quality of Tuberose (Polianthes tuberosa L. ‘Pearl’) Cut Flowers

“…In the cut flowers of tuberose, wilting and burning of florets and bending of the tips of flower spikes are the major problems that reduce the vase life of cut flowers (Jowkar & Salehi 2005). Various factors such as ethylene sensitivity, bacterial contamination, vascular blockage, and oxidative stress cause petal burning or browning, and floret wilting or abscission in cut flowers (Rubinstein 2000;Sankhla et al 2003;Rattanawisalanon et al 2003;Rogers 2006;Zhang et al 2011;Shahri & Tahir 2011). Moreover, various agents such as microbial activities, air obstruction and physiological response to cutting wound, gum aggregation in xylem, latex leakage, and other processes in the wound lead to vascular blockage and prevent water uptake, which reduces the freshness of cut flowers (Rattanawisalanon et al 2003;van Ieperen et al 2002;van Meeteren et al 2005;van Meeteren et al 2006;Imsabai et al 2013).…”