Studies On Cytokinins And Related Gene Expression During Tuberous Root Thickening In Ficus Microcarpa L.f.

In this experiment, tuberous roots of Ficus microcarpa were used as the materials for the research on the differences of cytokinin concentrations and expressions of cytokinin-related genes during thickening stage of tuberous roots, aimed to study the relationship between cytokinin-related metabolic enzyme genes and concentrations of cytokinin, and discuss the reasons caused the cytokinin concentration variations among different parts of the tuberous roots. The main results were summarized as follows:1. Concentrations of t-Z and t-ZR in tuberous roots were detected by HPLC. The results showed that t-ZR contents of dilated parts and root tips were significantly higher than those of others, and the contents were maximum at late thickening period; The contents of t-Z and t-ZR in the tuberous roots increased along with the thickening during the development of Ficus microcarpa. The contents of t-Z were grew rapidly at early thickening period of tuberous roots, and gradually slowed later. The contents of t-ZR grew slowly in early thickening period, then grew rapidly later. The contents of cytokinin in the root tips whose diameters were less than1.1mm were higher than those in the dilated parts.2. Actin1gene of Ficus microcarpa was cloned through homology cloning method, its cDNA full-length was1757bp, and its ORF which encoded377amino acids was1134bp, the sequence submission number in GenBank is JQ820243. The IPT gene of Ficus microcarpa was cloned and its cDNA segment was223bp which encoded74amino acids, submission number in GenBank is JQ820244. The CKX gene of Ficus microcarpa was cloned and its cDNA segment was491bp which encoded163amino acids, submission number in GenBank is JQ820245.3. Fluorescence quota PCR was used to carry on the quantitative analysis, the results showed that Actin1gene expressed stablely at transcript level in the tuberous roots of Ficus microcarpa, therefore, Actin1gene could be used as reference gene to detect other target genes transcriptional expression during tuberous root thickening. The results showed that transcription level of IPT gene was increased in pace with the thickening of tuberous roots of Ficus microcarpa. The transcriptional expression of CKXgene was first drop and then upward during the thickening period of tuberous roots, transcriptional level was decreased at early thickening period, and increased at late thickening period. The study suggested that cytokinin biosynthesis depended on the expressions of key enzymes of cytokinin metabolism genes, which affected cytokinin accumulations.