Functional analysis of an iaaM gene in parthenocarpic fruit development in transgenic Physalis pubescens L. plants

Abstract

An efficient somatic embryogenesis system for Physalis pubescens L. (husk tomato) was developed prior to transformation. Subsequently, cotyledonary explants of P. pubescens were transformed with a chimeric construct containing an iaaM gene from driven by the fruit-specific promoter 2A12 to develop parthenocarpic fruits. Following selection of explants on Murashige and Skoog (MS) medium containing containing 75 mg l−1 kanamycin (Km), 36 km-resistant callus clusters were recovered, and these were regenerated into whole plants. Expression of the iaaM gene was detected in confirmed transgenic fruits. The 0.9-kb 2A12 promoter was capable of directing expression of the introduced iaaM gene in transgenic P. pubescens fruits, but iaaM expression was absent from both leaves and flowers. Quantitative measurements of indole-3-acetic acid (IAA) content during fruit development indicated that the IAA levels in transgenic lines increased from anthesis through young fruits and peaked at fruit maturity. On average, IAA contents in transgenic fruits were two-fold higher than those in control fruits. Under greenhouse condition, vegetative growth, morphology, and the flowering of transgenic plants were comparable to those of control plants. However, the fruits of transgenic lines ripened earlier and had fewer seeds per fruit than did control plants.