A Study On MicroRNA-mediated Mechanisms Of Adventitious Roots Growth And Antioxidant In Submergenced Maize Seedlings

Mo17, an inbred line of Zea mays sensitive to submergence, was used as the experimental material in this study in order to reveal the adaptative mechanism in the submerged maize seedlings. The microarray data showed that the expression levels of many of microRNAs (miRNAs) were significantly altered and also suggested that the submergence-responsive miRNAs were potentially involved in the regulation of morphological and metabolic adaptations in maize root cells. Based on the miRNA expression profiles and the functions of miRNA targets, the stress-responsive miRNAs could be involved in three pathways to reprogramme complex procedures of metabolism and physiology. Up-regulated zma-miR167 directly targetd cleavage of ARF12, ARF17 and/ or ARF25 mRNAs, and then affected the hormone homeostasis and signal pathways that induced repression of root elongation and activation of formation of adventitious root. Accumulation of SOD and ALDH due to decreasing of osa-miR528-like would aid elimination of reactive oxygen species and acetaldehyde under oxygen-deficient conditions. In this research, the result proved the two potential pathways.1. IAA homeostasis was disturbed in root cells of maize seedlings under submergence. The accumulation of the IAA enhanced the expression level of the zma-miR167. zma-miR167 negatively regulated the predicted gene ARF17 through interacting with the AGO1. ARF17 repressed the expression of the downstream target gene GH3 that changed the IAA content. Production of IAA induced the expression of downstream gene ra2. In addition, the adventitious roots were initiated in the submerged maize seedlings.2. The results from RT-PCR, the isoenzyme analysis and enzyme activity indicated that the transcriptional level of SOD was increased that enhanced SOD enzyme activity. These expression profiles showed the negative regulation patterns of the target gene by miRNA osa-miR528-like that agreed with the previous hypothesize. On earlier stage of submerged treatment, the plant initiated the expression of SOD when it sensed the environmental stimulate. SOD enzyme expression and its activity were accumulated in the translational level that eliminated the deleterious substances such as ROS in the anaerobic stress. On later stage of submerged stress, the SOD enzyme activity was reduced, in turn, resulted in decrease of vigor of root cells.The microRNA-mediated adaptative mechanism could improve the viability of the maize under submergence stress condition.