Abstract
BackgroundMineral fertilization and pest control are essential and costly requirements for modern crop production. The two measures go hand in hand because plant mineral status affects plant susceptibility to pests and vice versa. Nutrient deficiency triggers specific responses in plants that optimize nutrient acquisition and reprogram metabolism. K-deficient plants illustrate these strategies by inducing high-affinity K-uptake and adjusting primary metabolism. Whether and how K deficient plants also alter their secondary metabolism for nutrient management and defense is not known.ResultsHere we show that K-deficient plants contain higher levels of the phytohormone jasmonic acid (JA), hydroxy-12-oxo-octadecadienoic acids (HODs) and 12-oxo-phytodienoic acid (OPDA) than K-sufficient plants. Up-regulation of the 13-LOX pathway in response to low K was evident in increased transcript levels of several biosynthetic enzymes. Indole and aliphatic glucosinolates accumulated in response to K-deficiency in a manner that was respectively dependent or independent on signaling through Coronatine-Insensitive 1 (COI1). Transcript and glucosinolate profiles of K-deficient plants resembled those of herbivore attacked plants.ConclusionsBased on our results we propose that under K-deficiency plants produce oxylipins and glucosinolates to enhance their defense potential against herbivorous insects and create reversible storage for excess S and N.
Highlights
Mineral fertilization and pest control are essential and costly requirements for modern crop production
Oxylipin concentrations rise in response to low K Using liquid chromatography-mass spectrometry (LCMS) [28] we identified jasmonic acid (JA) and several other oxylipins in leaves of A. thaliana
The largest increase was found for oxo-phytodienoic acid (OPDA) (> 5-fold), the smallest for JA (1.8-fold)
Summary
Mineral fertilization and pest control are essential and costly requirements for modern crop production. Application of fertilizers and pesticides is common practice in modern agriculture to ensure the growth and health of crops Both measures present substantial costs to food production and to the environment. Many secondary metabolites produced by plants act as toxins and deterrents for pests and pathogens. Since they are often rich in N and/or S deficiency in N or S impacts on the biosynthesis of these compounds and on the defense potential of plants [4,5]. JA biosynthesis occurs through the octadecanoid acid pathway, which starts from the oxidation of polyunsaturated fatty acids by lipoxygenase and produces a number of intermediate oxylipins [9,10] Several of these have signal function and antimicrobial properties [11]. Our previous finding that a large part of the K-dependent transcriptome is absent or replaced in A. thaliana coi mutants is further support for a role of JA in plant responses to K-supply [18]
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