Fig. 2.

Modulation of plant-pathogen defense responses by mineral limitation. Increasing evidence indicates that nutritional status has an impact on plant defense. In Arabidopsis, phosphate limitation can modulate defense signaling either via the jasmonic acid (JA) pathway or via PHR1, a master regulator that governs responses to phosphate starvation. PHR1 has a dual function of modulating the plant immune system, either by inhibiting the expression of salicylic acid (SA)-dependent genes or by activating a subset of JA-responsive genes that are mainly involved in glucosinolate biosynthesis (Castrillo et al., 2017). Low potassium leads to opposite responses in Arabidopsis, barley, and rice (Armengaud et al., 2010; Shankar et al., 2013). Although low potassium leads to an increased level of JA and expression of JAZs genes in Arabidopsis and barley, a decreased level of JA occurs in rice. Upon low nitrate conditions, genes belonging to the WRKY transcription factor family are induced in Arabidopsis (Patterson et al., 2010), which in turn can regulate the SA/JA balance as well as hormone-related gene expression. Interestingly, a direct interaction between NLA and ORE1, two key regulators of nitrogen limitation and senescence, has recently been demonstrated. ORE1 is a NAC transcription factor (NAC092) that might modulate JA-dependent gene expression (Park et al., 2018).