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Involvement of papain and legumain proteinase in the senescence process of M edicago truncatula nodules
Author(s) -
Pierre Olivier,
Hopkins Julie,
Combier Maud,
Baldacci Fabien,
Engler Gilbert,
Brouquisse Renaud,
Hérouart Didier,
Boncompagni Eric
Publication year - 2014
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.12717
Subject(s) - senescence , medicago truncatula , nodule (geology) , biology , microbiology and biotechnology , vacuole , cytoplasm , botany , biochemistry , symbiosis , genetics , bacteria , paleontology
Summary The symbiotic interaction between legumes and R hizobiaceae leads to the formation of new root organs called nodules. Within the nodule, R hizobiaceae differentiate into nitrogen‐fixing bacteroids. However, this symbiotic interaction is time‐limited as a result of the initiation of a senescence process, leading to a complete degradation of bacteroids and host plant cells. The increase in proteolytic activity is one of the key features of this process. In this study, we analysed the involvement of two different classes of cysteine proteinases, M t CP 6 and M t VPE , in the senescence process of M edicago truncatula nodules. Spatiotemporal expression of M t CP 6 and M t VPE was investigated using promoter– β‐glucuronidase fusions. Corresponding gene inductions were observed during both developmental and stress‐induced nodule senescence. Both M t CP 6 and M t VPE proteolytic activities were increased during stress‐induced senescence. Down‐regulation of both proteinases mediated by RNA i in the senescence zone delayed nodule senescence and increased nitrogen fixation, while their early expression promoted nodule senescence. Using green fluorescent protein fusions, in vivo confocal imaging showed that both proteinases accumulated in the vacuole of uninfected cells or the symbiosomes of infected cells. These data enlighten the crucial role of M t CP 6 and M t VPE in the onset of nodule senescence.