Cloning And Function Analysis Of KdSOC1 In Kalanchoe Daigremontiana

Kalanchoe daigremontiana utilizes plantlet formation between its zigzag leaf margins as its method of asexual reproduction. In this study, K. daigremontiana SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (KdSOC1), a key intermediate in the transition from vegetative to asexual growth, was cloned. And its expression profiles during plantlet formation under different environmental and hormone induction conditions were analyzed. Furthermore, optimization in Kalanchoe daigremontiana genetic transformation system. The main conclusions are as follows:1 The full-KdSOC1 cDNA sequence length was 1410bp with 70% shared homology with Carya cathayensis SOC1. The possible ORF sequence length was 684bp, which encoded 227 amino acids. The conserved domain search found an MADS-MEF2-like domain and a K-box domain in the KdSOC 1 amino acid sequence.2 The full-KdSOC1 promoter sequence was 1401bp long and contained multiple-hormone-responsive cis-acting elements, which including an ABA responsive element (ABRE), an MeJa-responsive element (CGTCA-motif), a GA-responsive element (GARE-motif), and an SA-responsive element (TCA element), and rbcS-CMA7a (a light responsive element)、TATA-box (core promoter element) and CAA-box (common cis-acting element in promoter and enhancer regions).3 Hormone induction assays showed that gibberellins and salicylic acid mainly regulated KdSOCl expression. The swift change from low to high KdSOCl expression levels during long-day induction was accompanied by the rapid emergence of plantlets. Drought stress stimulated KdSOC1expression in leaves both with and without plantlet formation. Together, the results suggested that KdSOC1 was closely involved in environmental stimulation signal perception and the transduction of K. daigremontiana plantlet formation.4 Attempts to identification of KdSOC1 functions, the overexpression vector pBIN438-ORF KdSOC1, RNAi vector pZH01-AS ORF kdSOC1-GUS-S ORFkdSOC1 and promoter vector pBI121-PromoterkdSOC1 GUS was successfully constructed, and these vectors transformed into K. daigremontiana by using Agrobacterium tumefaciens.5 Stem, young leaf and mature leaf of K.daigremontiana were used as explants and MS medium to examine the effect of different concentrations 6-BA and 2,4-D on callus induction, and through embryogenic callus rate and callus browning rate to determine the optimal induction hormone proportion. The results of the study show that the optimal hormone concentration ratio for stem callus induction was 0.5mg/L 6-BA:0.5mg/L 2,4-D and embryogenic callus rate was 55.56%; the optimal hormone concentration ratio for young leaf callus induction was 1mg/L 6-BA:1.5mg/L 2,4-D and embryogenic callus rate was 29.92%; the optimal hormone concentration ratio for mature leaf callus induction was 2.5mg/L 6-BA:0.5mg/L 2,4-D and embryogenic callus rate was 43.07%. So the stem section and mature leaf are ideal materials to induce tetraploid callus formation air plant.