Knockout of Arabidopsis thaliana VEP1 , Encoding a PRISE (Progesterone 5β-Reductase/Iridoid Synthase-Like Enzyme), Leads to Metabolic Changes in Response to Exogenous Methyl Vinyl Ketone (MVK)

Small or specialized natural products (SNAPs) produced by plants vary greatly in structure and function, leading to selective advantages during evolution. With a limited number of genes available, a high promiscuity of the enzymes involved allows the generation of a broad range of SNAPs in complex metabolic networks. Comparative metabolic studies may help to understand why-or why not-certain SNAPs are produced in plants. Here, we used the wound-induced, vein patterning regulating ( StR1, At4g24220) and its paralogue gene on locus At5g58750 ( StR2) from to study this issue. The enzymes encoded by -like genes were clustered under the term PRISEs (progesterone 5β-reductase/iridoid synthase-like enzymes) as it was previously demonstrated that they are involved in cardenolide and/or iridoid biosynthesis in other plants. In order to further understand the general role of PRISEs and to detect additional more "accidental" roles we herein characterized steroid reductase 1 ( StR1) and compared it to steroid reductase 2 ( StR2). We used Col-0 wildtype plants as well as knockout mutants and knockout mutants overexpressing either StR1 or StR2 to investigate the effects on vein patterning and on the stress response after treatment with methyl vinyl ketone (MVK). Our results added evidence to the assumption that StR1 and StR2, as well as PRISEs in general, play specific roles in stress and defense situations and may be responsible for sudden metabolic shifts.