Regulation of the maize (Zea mays L.) embryo proteome by RTCS which controls seminal root initiation

Seminal roots are initiated at the scutellar node during maize (Zea mays L.) embryo development. The maize mutant rtcs (rootless concerning crown and seminal roots) does not initiate seminal roots while its wild-type siblings form on average 2.9 seminal roots per seedling. In this study, proteome profiles of 25-day-old immature maize embryos were compared between wild-type and rtcs plants via two-dimensional electrophoresis (2-DE). Electrospray ionization tandem mass spectrometry (ESI-MS/MS) identified 23 proteins encoded by 21 different genes that were differentially accumulated between wild-type and rtcs embryos (Fc> or =2; FDR<10%). Among the differentially accumulated proteins, two isoforms of a phosphoglycerate kinase and a malate dehydrogenase were preferentially accumulated in wild-type embryos. Both enzymes are related to the generation of energy-rich ATP or NADPH molecules and are crucial checkpoints of cellular energetics in plants. Comparison of embryonic proteins differentially accumulated between wild-type and rtcs embryos revealed little overlap with proteins differentially accumulated between wild-type and rum1 embryos which also do not initiate seminal roots. This might be due to distinct influences of RTCS and RUM1 on the composition of the embryo proteome, but could also be explained by different stages of embryo development that were analyzed in these studies.