The Analysis of Leaf Senescence
As can be read on other parts of the site, the senescence process is programmed and enables the retention of a plants nutrients. It is an age dependent process that is under the influence of external and internal processes, and allows transfer of nutrients from areas where they are no longer required to areas of cell development. Many things can be used to assay senescence biologically including measuring the activity of genes, proteins and membrane ions.
Many mutants have been identified that are involved in senescence in Arabidopsis; this enables genes to be identified that play a role in senescence processes. To identify candidates, mutant screens were developed that identified plants that had both delayed and early senescence (reverse and forward genetics). Another method to identify genes involved in senescence is to measure the expression levels of genes that are undergoing leaf senescence by the use of molecular techniques such as RT-PCR, microarrays and Northern Blotting. Although both of these methods lead to identification of genes involved in senescence, they also identify many false candidates, as genes may be upregulated as a secondary process following senescence or involved in roles such as homeostasis.
Genes identified in senescence
The use of microarray technology in the study of senescence processes has identified over 800 candidate genes in Arabidopsis. Additionally DNA microarrays have been used to look at leaf senescence in the tree Aspen. When looking at developmental processes it is interesting to look at the genes that may be involved in underlying these processes such as transcription factors and those that encode signal transduction regulators. Many of the genes that have been identified as differentially regulated during leaf senescence have mutants available from T-DNA insertion lines such as those available from SALK and GABBI. This has allowed the effect of mutations of differentially regulated genes during senescence to be further analysed and better understood.
Buchanan-Wollaston et al. (2005). Comparative transcriptome analysis reveals significant differences in gene expression and signalling pathways between developmental and dark/starvation-induced senescence in Arabidopsis. Plant Journal. 42:567 to 585.
Lim et al. (2007) Leaf Senescence. Annual Review of Plant Biology. 58: 115 to 136.
van der Graaff et al. (2006). Transcription analysis of Arabidopsis membrane transporters and hormone pathways during developmental and induced leaf senescence. Plant Physiolgy. 141: 776 to 92.