Large‐scale identification of leaf senescence‐associated genes

Abstract

SummaryLeaf senescence is a form of programmed cell death, and is believed to involve preferential expression of a speci®c set of`senescence-associated genes' (SAGs). To decipher the molecular mechanisms and the predicted complex network of regulatory pathways involved in the senescence program, we have carried out a large-scale gene identi®cation study in a reference plant, Arabidopsis thaliana. Using suppression subtractive hybridization, we isolated approximately 800 cDNA clones representing SAGs expressed in senescing leaves. Differential expression was con®rmed by Northern blot analysis for 130 non-redundant genes. Over 70 of the identi®ed genes have not previously been shown to participate in the senescence process. SAGencoded proteins are likely to participate in macromolecule degradation, detoxi®cation of oxidative metabolites, induction of defense mechanisms, and signaling and regulatory events. Temporal expression pro®les of selected genes displayed several distinct patterns, from expression at a very early stage, to the terminal phase of the senescence syndrome. Expression of some of the novel SAGs, in response to age, leaf detachment, darkness, and ethylene and cytokinin treatment was compared. The large repertoire of SAGs identi®ed here provides global insights about regulatory, biochemical and cellular events occurring during leaf senescence.

Gene expression in opening and senescing petals of morning glory (Ipomoea nil) flowers

“…Both an alcohol dehydrogenase (ADH), with a different sequence than our In17, and a so-called lipid transfer protein (LTP), which showed low similarity to In30, have been identified as SAGs in Arabidopsis leaves (Gepstein et al 2003). The role of ADH during senescence is as yet unclear.…”

Activity Profiling of Papain-Like Cysteine Proteases in Plants

“…The AALP and RD21 transcripts have been shown to accumulate during leaf senescence (Gepstein et al, 2003). To test whether the corresponding activity of these proteases also increases, we performed protease activity profiling on mature and senescing leaves and analyzed biotinylated proteins with anti-AALP and anti-RD21 antibodies.…”

“…In many cases, proposed functions for proteases have been inferred from the observed differential expression of their mRNAs (e.g. Zhao et al, 2000;Gepstein et al, 2003). The progress in assigning roles for proteases, however, is significantly impeded by their redundancy and posttranslational regulation.…”

A Novel Nuclear-Localized CCCH-Type Zinc Finger Protein, OsDOS, Is Involved in Delaying Leaf Senescence in Rice

“…During senescence, leaf cells undergo dramatic changes in cellular metabolism and a sequential degeneration of cellular structures (Nam, 1997). Previous efforts to elucidate the underlying molecular mechanism of leaf senescence began with the identification of senescenceassociated genes (SAGs; defined as genes with expression up-regulated during leaf senescence), and most of them are found to encode proteases, nucleases, lipases, hydrolases, enzymes involving nutrient recycling, stressresponsive proteins, and transcriptional regulators (Nam, 1997;Quirino et al, 2000;Buchanan-Wollaston et al, 2003;Gepstein et al, 2003;Lin and Wu, 2004).…”