Optimization of a virus-induced gene silencing system and functional elucidation of MaBAM9b in postharvest banana fruits
Abstract Background: Banana is a typical starch conversion fruit, and fruit ripening involves a process of fruit quality formation. To improve the nutritional value of banana, it is necessary to understand the genetic basis of the metabolic pathways that operate during fruit ripening processes. MaBAM9b is a key enzyme gene that might play an important role in starch degradation during the banana fruit ripening process. The identification of gene function by stable genetic transformation is time- and energy-consuming. Thus, developing an efficient and rapid method for functional identification is imperative. Virus-Induced Gene Silencing (VIGS) is a reverse-genetics method based on RNA-mediated antiviral plant defense that has been used to rapidly identify gene function in plants. Results: In this report, 0.5% iodine-potassium-iodide (I2-KI) staining for 150 s determined that a 1:3 ratio of TRV1: TRV2-MaBAM9b cultivated at an optical density of 600 nm (OD600) 0.8 at 30 mmHg for 30 sec and kept on Murashige & Skoog (MS) media for 5 d produced the best silencing results. Under these conditions, the total starch content was greatly increased, while the β-amylase activity, soluble sugar contents, and the expression of endogenous MaBAM9b were greatly decreased. Conclusions: The developed system is particularly useful for studying genes and networks for starch conversion in fruit, which alone would not produce a visual phenotype. This system will provide a platform for banana functional genomics and for banana fruit quality improvement.