Abstract
Leaf senescence is the final stage of leaf development and is induced by the gradual occurrence of age-related changes (ARCs). The process of leaf senescence has been well described, but the cellular events leading to this process are still poorly understood. By analysis of progressively ageing, but not yet senescing, Arabidopsis thaliana rosette leaves, we aimed to better understand processes occurring prior to the onset of senescence. Using gene expression analysis, we found that as leaves mature, genes responding to oxidative stress and genes involved in stress hormone biosynthesis and signalling were up-regulated. A decrease in primary metabolites that provide protection against oxidative stress was a possible explanation for the increased stress signature. The gene expression and metabolomics changes occurred concomitantly to a decrease in drought, salinity, and dark stress tolerance of individual leaves. Importantly, stress-related genes showed elevated expression in the early ageing mutant old5 and decreased expression in the delayed ageing mutant ore9. We propose that the decreased stress tolerance with age results from the occurrence of senescence-inducing ARCs that is integrated into the leaf developmental programme, and that this ensures a timely and certain death.
Highlights
We propose that the decreased stress tolerance with age results from the occurrence of senescence-inducing age-related change (ARC) that is integrated into the leaf developmental programme, and that this ensures a timely and certain death
Leaf development is achieved through ARCs and, concomitant with its emergence, expansion, and maturation, the increase in leaf age leads to the progressive decline of cell and tissue function and eventually leaf senescence (Caswell and Salguero-Gomez, 2013; Kanojia and Dijkwel, 2018) It is possible that some ARCs play specific roles in ageing and the induction of senescence and here we term such changes as senescence-inducing ARCs
Arabidopsis wild type (WT) Ler-0 plants were grown in a long-day photoperiod and the first leaf pair of the rosette was harvested at 10 days after germination (DAG)
Summary
Ageing is an essential part of the normal plant developmental programme,whereby sequential changes occur during the plants’ life, from germination to senescence and death. The progressive changes that occur during plant development are termed age-related changes (ARCs) (Jing et al, 2005; Jibran et al, 2013; Kanojia and Dijkwel, 2018). Examples of visible ARCs in plants are the transition of juvenile to adult leaves, the initiation of the reproductive phase, and the yellowing of senescing leaves. Leaf development is achieved through ARCs and, concomitant with its emergence, expansion, and maturation, the increase in leaf age leads to the progressive decline of cell and tissue function and eventually leaf senescence (Caswell and Salguero-Gomez, 2013; Kanojia and Dijkwel, 2018) It is possible that some ARCs play specific roles in ageing and the induction of senescence and here we term such changes as senescence-inducing ARCs
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