Convergence and divergence in gene expression profiles induced by leaf senescence and 27 senescence-promoting hormonal, pathological and environmental stress treatments.

In addition to age and developmental progress, leaf senescence and senescence-associated genes (SAGs) can be induced by other factors such as plant hormones, pathogen infection and environmental stresses. The relationship is not clear, however, between these induced senescence processes and developmental leaf senescence, and to what extent these senescence-promoting signals mimic age and developmental senescence in terms of gene expression profiles. By analysing microarray expression data from 27 different treatments (that are known to promote senescence) and comparing them with that from developmental leaf senescence, we were able to show that at early stages of treatments, different hormones and stresses showed limited similarity in the induction of gene expression to that of developmental leaf senescence. Once the senescence process is initiated, as evidenced by visible yellowing, generally after a prolonged period of treatments, a great proportion of SAGs of developmental leaf senescence are shared by gene expression profiles in response to different treatments. This indicates that although different signals that lead to initiation of senescence may do so through distinct signal transduction pathways, senescence processes induced either developmentally or by different senescence-promoting treatments may share common execution events.