Strigolactones and auxin cooperate to regulate lateral root development in response to nitrate

In maize, nitrate regulates root development thanks to the coordinated action of many players. In this study, the involvement of SLs and auxin as putative downstream components of the nitrate regulation of lateral root development was investigated. To this aim, the endogenous SL content of maize root in response to nitrate availability was assessed by means of LC-MS/MS and measurements of lateral root density in the presence of analogues or inhibitors of auxin and strigolactones were performed. Furthermore, un untargeted RNA-seq based approach was used to better characterize the participation of auxin and strigolacotones to the transcriptional signature of maize root response to nitrate. Our results suggested that N deprivation toughly induces zealactone and carlactonoic acid biosynthesis in maize root, to a higher extent if compared to P-deprived roots. Moreover, data on lateral root density led to hypothesise the existence of both auxin-dependent and auxin-independent effects of nitrate on LR development. In addition, the inhibition of SL biosynthesis seems to participate to the auxin-dependent induction of LR, but the involvement of further downstream unknown components cannot be ruled out. Illumina RNA-Seq analysis of maize roots collected from seedlings grown for 24 h in nutrient solution supplied with NO3-, TIS108 and NO3- plus PCIB compared to negative controls grown in a N-deprived nutrient solution. 3 days old maize B73 inbreed seedlings were treated for 24 h prior to roots collection and RNA extraction. 3 biological replicates per condition were produced, each composed by 4-8 plants.