Isolation of high-quality total RNA from floral organs of pineapple guava (Feijoa sellowiana Berg.)

Pineapple guava (Feijoa sellowiana Berg.) is a great commercial plant for its fruit quality and unique flavor. Some key genes expressed in floral organs play significant roles in governing the transition from the juvenile to the adult stage. To clone these genes, high-quality RNA of floral organs were required. In this study, total RNAs were isolated and compared from pineapple guava floral organs with four approaches including guanidine isothiocyanate-based method, SDS-based method, RNA purification kit-method and improved CTAB-based method. The results showed that high-quality total RNA was acquired only by the improved CTAB-based method but not by the other three methods. Integrity examination of total RNA by agarose gel electrophoresis revealed that three RNA strips (28S, 18S, 5.8S) were clear and bright. Anlysis with spectrophotometer showed that the A260/A280 absorbance ratio was 1.9037, suggesting that the RNA was not contaminated by DNA and protein. The total RNA was applied for RT-PCR and an approximately 350 bp-sized fragment was successfully amplified. Extraction, cloning and sequencing indicated that a MADS-box gene was identified. The results suggested that the total RNA isolated by the improved CTAB-based method is of high-quality that can be used in RT-PCR or RACE-PCR for cloning of important genes expressed in floral organs.