Identification of the new growth regulatory gene in maize (Zea mays L.)

The aim of this research is to identify new growth regulatory genes in maize. Plant growth is the results of cell division and cell expansion and the maize leaf offers a powerful system to investigate these processes since they take place in distinct developmental zones along the axis of a single leaf. The basal part of leaf consists of the meristematic zone of dividing cells, followed by elongation zone in which cells elongate and finally the most distal part containing mature cells. We used microarray analysis on these leaves to identify genes specific to each developmental stage. Our main focus is on the genes specifically upregulated in the meristematic zone since these might represent new growth regulators. In this cluster, an overrepresentation of chromatin genes is detected. Therefore, mutants from the Chromatin Database were screened for leaf growth phenotypes. The RNAi line for the DNA METHYLTRANSFERASE103 (DMT103) showed significantly shorter leaves and reduced leaf elongation rate. To further unravel this growth effect, we performed a kinematic analysis showing that cell expansion rather than cell production was affected in the mutant compared to wild type. This corresponds to the expression profile of the gene, which is low in the meristem and very high in the mature zone. Those findings were also correlated by expression analysis of cell cycle genes thus most of the genes? expression did not change significantly. Flow cytometry showed the proportion of the DNA amount was also stayed unchanged meaning. It was also observed that the primary root was affected in the mutant ones. Line05 was also treated cold and drought to see whether DMT103 have function to tolerate that kind of stress. It was seen that DMT103 did not play role in drought but had function in cold stress. Expression analysis was done whether to see the other DMT family members were affected and it was found that two other members of the family were significantly down regulated in mutant ones. Nevertheless, our data clearly demonstrate the feasible role of DMT103 gene for growth regulation.