Molecular analysis of natural leaf senescence in Arabidopsis thaliana

Abstract

Molecular analysis of natural leaf senescence in Arabidopsis ihaliana. -Physiol. Plant. 92: .^22-328,We have analyzed macromoleeuiar changes that are associated with natural leaf senescence in Arabidopsis thaliana. The loss of chlorophyll that is characteristic of leaf senescence is accompanied by a specific pattem of decline of total RN.A and protein ievels. We have construcled two cDNA libraries representing mR.NAs from .\rabidopsis leaves at different senescence stages. Six cDNA clones corresponding to mRNAs that substantially increase in abundance during senescence were isolated. The levels of these niRiN As remain e!e\ ated into the tate stages of senescence when most of the chlorophyll and protein of the leaf has been degraded. Sis cDNA clones that correspond to mRNAs that e,xhibit contrasting behavior were also identified: the levels of these mRNAs decrease to undetectable levels during senescence. The changes in the levels of these specific mRNAs during the course of senescence are presented. The results indicate that major ehanges in gene expression occur in ,Arahidiipsis leaves during the process of senescence.

Overexpression of a LAM Domain Containing RNA-Binding Protein LARPIc Induces Precocious Leaf Senescence in Arabidopsis

“…Inducible overexpression of LARP1c elevates transcript levels of SAGs and defense-related genes To confirm that LARP1c plays an important role in regulating leaf senescence, we analyzed the expression of several SAGs in the 1c-DEX transgenic lines after DEX induction for 24 and 48 h, before the transgenic plants showed signs of chlorosis. In parallel with LARP1c overexpression, increased expression of several SAGs, including SAG13 (Lohman et al, 1994), SEN4 (Park et al, 1998), and WRKY6 (Robatzek and Somssich, 2001), were observed (Fig. 6).…”

Large‐scale identification of leaf senescence‐associated genes

“…Expression of many genes associated with photosynthetic activity and other anabolic processes is downregulated during leaf senescence (Gepstein, 1988), whereas others are upregulated. Indeed, several dozen genes upregulated during senescence, designated as senescence-associated genes (SAGs) have been identi®ed in various species (BuchananWollaston and Ainsworth, 1997;Dangl et al, 2000;Lee et al, 2001;Lohman et al, 1994;Nam, 1997). The function of the predicted SAGs' products may give a clue to the biochemical, regulatory, and cellular pathways of senescence.…”

“…The downregulation of a certain set of genes on the one hand, and the upregulation of others on the other hand, re¯ect not only the transition from autotrophic to heterotrophic metabolism, but also the induction of de novo synthesis of enzymes participating in the self-destruction process that eventually causes death. Among the prominent SAGs are genes responsible for the execution of the senescence syndrome encoding degradative enzymes: proteinases (Dangl et al, 2000;Lohman et al, 1994;Thompson et al, 1998Thompson et al, , 2000, lipases (Thompson et al, 1998, nucleases (Lers et al, 2001;Rubinstein, 2000), chlorophyllases (Jacob-Wilk et al, 1999), and enzymes for nutrient recycling such as glutamate synthase (Watanabe et al, 1994). Recently, a few senescence-associated regulatory genes have been identi®ed.…”

Identification of three genetic loci controlling leaf senescence in Arabidopsis thaliana

“…a relatively reproducible leaf senescence pattern (Hensel et al, 1993;Lohman et al, 1994) together with a short life span, and is readily amenable to genetic analysis. Thus, Introduction we chose Arabidopsis as a model system for genetic Leaf development ends with senescence, consisting of screening of delayed leaf senescence mutants.…”

“…However, we equalized the leaf age in all the following experiments to avoid the effects Although chlorophyll loss and the concomitant yellowing of leaves are convenient and distinctive indications of of age differences of the leaves in the mutant plants. leaf senescence, this phenotype can be uncoupled from 'functional' leaf senescence (Smart, 1994). For example,…”