Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 15, 2011
Publication Date: April 25, 2012
Citation: Rijavec, T., Li, Q., Dermastia, M., Chourey, P.S. 2012. Cytokinins in developing maize caryopsis and their possible role in seed size determination. Plant Physiology. 13:293-308. Technical Abstract: Quantitative measurements of the total nine CK metabolites showed that the genotypes with reduced levels of invertase activity have reduced concentration of the metabolically inactive CK form zeatin-9-glucoside and increased concentration of active CK ribosides. Quantitative real-time PCR analyses for the CK genes showed that the cytokinin-N-glucosyl transferase gene (ZmCngt1) was expressed at the highest level at 10 DAP and were greatly reduced in expression in the mn1 mutant. Additionally, this study supports our model (Rijavec et al. 2009) which proposes that high amount of CK (Fig 1) and higher ratio of their active forms may partially compensate the INCW2-deficiency in regulating CycD3 and CycD2 induced cell divisions by CKs and sucrose in the mn1 endosperm. While glucose and sucrose are reduced, and sucrose level is higher between 12 and 20 DAP in the lower part of the caryopsis, probably because of the INCW2 deficiency. Consistently with the model, the sink strength is greater in the Mn1. In contrast, the level of glucose, fructose and sucrose was, higher in the upper part of the mutant caryopsis, due to yet unknown mechanisms, and may contribute to the increase expression of the CycD3 gene and to normal, although substantially slower development of mn1.