Nitrogen metabolism meets phytopathology

Abstract

Nitrogen (N) is essential for life and is a major limiting factor of plant growth. Because soils frequently lack sufficient N, large quantities of inorganic N fertilizers are added to soils for crop production. However, nitrate, urea, and ammonium are a major source of global pollution, because much of the N that is not taken up by plants enters streams, groundwater, and lakes, where it affects algal production and causes an imbalance in aquatic food webs. Many agronomical data indicate that the higher use of N fertilizers during the green revolution had an impact on the incidence of crop diseases. In contrast, examples in which a decrease in N fertilization increases disease severity are also reported, indicating that there is a complex relationship linking N uptake and metabolism and the disease infection processes. Thus, although it is clear that N availability affects disease, the underlying mechanisms remain unclear. The aim of this review is to describe current knowledge of the mechanisms that link plant N status to the plant's response to pathogen infection and to the virulence and nutritional status of phytopathogens.

Plant nitrogen assimilation and its regulation: a complex puzzle with missing pieces

“…However, target genes are not always obvious [77], and cross-regulation with other nutrients [78 ], the involvement of hormone signaling [79] and the interaction with biotic stress [80] need to be taken into account. Considerable success in improving NUE may be expected from exploiting natural variation and quantitative genetic approaches.…”

Plant senescence and proteolysis: two processes with one destiny

“…Pathogen and pest lifestyles determine the developmental program of the host, and on the other side, the developmental status of the host may affect the outcome of the host-pathogen/pest interactions (Haffner et al , 2015). Pathogen infection and herbivore infestation influence leaf senescence via modulation of the plant metabolite status directly affecting primary metabolism or by regulating levels of plant hormones (Masclaux-Daubresse et al , 2010; Machado et al , 2013; Seifi et al , 2013, Fagard et al , 2014). …”

“…Likewise, induced-senescence genes have been detected during the hypersensitive response (HR) against incompatible bacteria and fungi as well as interactions with viruses (Pontier et al , 1999, Schenk et al , 2005, Espinoza et al , 2007, Fernandez-Calvino et al , 2015). The same SAGs were overexpressed during HR produced by fungal, bacterial and viral infection (Fagard et al , 2014). In Arabidopsis and grapevine, transcripts coding for aspartyl- and cysteine-protease (CysProt) increased during senescence and as a part of plant responses during compatible viral interactions (Espinoza et al , 2007).…”

“…Down-regulation of OsSAG12-1 in rice brings about early senescence and enhances cell death when inoculated with Xanthomonas oryzae (Singh et al , 2013). Biotic stresses mediated by pathogens induce N mobilization in Arabidopsis (Masclaux-Daubresse et al , 2010, Fagard et al , 2014). However, references about proteolysis in leaf senescence upon arthropod feeding are occasional.…”

Infection byRhodococcus fasciansmaintains cotyledons as a sink tissue for the pathogen

“…In addition to carbon, microbes require a source of nitrogen (Fagard et al, 2014). Pratelli and Pilot (2014) suggested that pathogen infection leads to changes in expression of genes involved in amino acid metabolism and transport.…”