Response of glucosinolate biosynthetic genes to K deficiency. Quantitative PCR analysis of transcript levels of glucosinolate biosynthesis genes in A. thaliana plants grown for 14 days on vertical Petri dishes containing control medium (black) or -K medium (white). Approximately 50 plants were pooled. Averages and standard error of technical replicates are shown, normalised to the expression level of the constitutive gene EF1alpha or YLS8 (see Material and Methods for qPCR details and Additional file 5 for primers). Stars indicate significant differences between control and K-starved plants at p < 0.05 (*) or p < 0.01 (**) as determined by t-test.