Arabidopsis onset of leaf death mutants identify a regulatory pathway controlling leaf senescence

Abstract

SummaryThe onset of leaf senescence is controlled by leaf age and ethylene can promote leaf senescence within a specific age window. We exploited the interaction between leaf age and ethylene and isolated mutants with altered leaf senescence that are named as onset of leaf death (old) mutants. Early leaf senescence mutants representing three genetic loci were selected and their senescence syndromes were characterised using phenotypical, physiological and molecular markers. old1 is represented by three recessive alleles and displayed earlier senescence both in air and upon ethylene exposure. The etiolated old1 seedlings exhibited a hypersensitive triple response. old2 is a dominant trait and the mutant plants were indistinguishable from the wild-type when grown in air but showed an earlier senescence syndrome upon ethylene treatment. old3 is a semi-dominant trait and its earlier onset of senescence is independent of ethylene treatment. Analyses of the chlorophyll degradation, ion leakage and SAG expression showed that leaf senescence was advanced in ethylene-treated old2 plants and in both air-grown and ethylene-treated old1 and old3 plants. Epistatic analysis indicated that OLD1 might act downstream of OLD2 and upstream of OLD3 and mediate the interaction between leaf age and ethylene. A genetic model was proposed that links the three OLD genes and ethylene into a regulatory pathway controlling the onset of leaf senescence.

Transcription Analysis of Arabidopsis Membrane Transporters and Hormone Pathways during Developmental and Induced Leaf Senescence

“…The importance of ET signaling during senescence is illuminated by a delayed senescence phenotype of ET-insensitive mutants like ein2 in Arabidopsis (Oh et al, 1997). However, ET is not essential for the onset and progression of senescence (Grbic and Bleecker, 1995;Jing et al, 2002).…”

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

“…It is possible that developmental cues or age-related factors could influence the age-dependent senescence by initiating the senescence program and further activating downstream signaling cascade, including the JA pathway. Similarly, onset of leaf death1 (OLD1) might function as a repressor for integrating ethylene action into leaf senescence, because the old1-1 mutant displayed a phenotype with an earlier onset of senescence, which was further accelerated by ethylene exposure in an age-dependent manner (Jing et al, 2002).…”

“…They are predicted to encode transcription factors such as WRKY6 (WRKY DNA-binding protein 6; Robatzek and Somssich, 2001) and WRKY53 (Hinderhofer and Zentgraf, 2001;Miao et al, 2004) in Arabidopsis (Arabidopsis thaliana), and receptor-like kinases such as the Arabidopsis SIRK (senescence-induced receptorlike kinase; Robatzek and Somssich, 2002) and the bean (Phaseolus vulgaris) SARK (senescence-associated receptor-like kinase; Hajouj et al, 2000). However, only a very limited number of the regulators were functionally confirmed through genetic approaches to date (Woo et al, 2001;Jing et al, 2002;Miao et al, 2004).…”

“…Cytokinins have been found to play a role in delaying leaf senescence (Gan and Amasino, 1995;McCabe et al, 2001;Kim et al, 2006), whereas ethylene, jasmonates (JAs), brassinosteroids, and salicylic acids are known to promote the process of senescence (Grbic and Bleecker, 1995;Oh et al, 1997;Morris et al, 2000;Jing et al, 2002;Yin et al, 2002). For example, JA could rapidly induce the expression of several SAGs (Park et al, 1998;Schenk et al, 2000).…”

ETHYLENE-INSENSITIVE3 Is a Senescence-Associated Gene That Accelerates Age-Dependent Leaf Senescence by Directly Repressing miR164 Transcription in Arabidopsis

“…Exogenous application of ethylene accelerates leaf senescence, and application of inhibitors of ethylene biosynthesis or action delays senescence (Wang et al, 2001). However, ethylene does not directly regulate the onset of leaf senescence but acts to modulate its progression (Jing et al, 2002(Jing et al, , 2005. Senescence is not readily induced by ethylene in young leaves, but ethylene can induce senescence in leaves that have reached a defined age (Jing et al, 2005).…”