The Complex Regulation of Senescence

Everybody is familiar with the visual aspects of plant senescence. Color changes occurring in senescing leaves are, however, only one (albeit striking) symptom of the senescence process. As this process usually leads to cell, tissue, organ or even organism death, its timing is critical for plant fitness and, in an agricultural setting, for crop performance. It is therefore necessary to understand the mechanisms regulating senescence onset and rate, especially at the organ and (for annual species) organism level. Considering the importance of senescence for plant fitness, it is unsurprising that it is influenced by many environmental and genetic factors, rendering its detailed analysis challenging. Numerous molecular and transcriptomic studies have provided us with extensive lists of "senescence-associated genes" or "SAGs," many of which may have functions in either the regulation or execution of senescence. Functional characterization has been initiated for a subset of SAGs, especially for transcription factors (mainly in the NAC/WRKY families) and protein kinases. A major challenge for senescence research is the efficient integration of available information (consisting of large -omic data sets and detailed single-gene/protein studies) into a more coherent picture, leading to new hypotheses and allowing us to address the most important open questions.