Inheritance of the genetic construct for RNA-silencing of the γ-kafirin gene (gKAF1) in the progeny of transgenic sorghum plants

Abstract

Sorghum is one of the most important cereal crops in drought regions of the Globe. However, a number of constrains, such as poor nutritional value compared to other cereals, which is caused by resistance of its grain storage proteins (kafirins) to protease digestion, makes it less popular. The use of modern genetic technologies, such as RNA interference, opens up prospects for solving this problem. In this paper, we describe the inheritance of the genetic construct for RNAi silencing of the γ-kafirin gene (gKAF1) in the progeny of the mutant Avans-1/18, that we obtained previously by Agrobacterium-mediated genetic transformation of immature embryos of commercial cv. Avans. Inheritance of the genetic construct was traced by PCR-analysis to the nos-promoter governing expression of the marker gene bar and to the ubi1-intron, which is part of the genetic construct for silencing. It was found that the genetic construct inherited in T1 and T2 generations of the mutant grown both in the growth chamber and in the field plot, and in the F1 hybrids of the mutant with CMS-lines A2 KVV-181, A2 KVV-114, A2 O-1237, and fertile lines Volzhskoe-4v, Volzhskoe-615, O-1237. The studied plants from T1 and T2 generations had significantly higher in vitro protein digestibility than original non-transgenic cv. Avans. The vitreous endosperm in these plants was reduced either completely or manifested a faint layer. These data demonstrated that genetic construct for gKAF1 silencing was not only stably integrated in genome of the mutant plants but also expressed and improved the digestibility of endosperm proteins. In addition, in T1 progeny we found the plant, PCR positive for nos-promoter but PCR-negative for ubi1-intron, that had vitreous endosperm and was characterized by poor in vitro protein digestibility. These data are an example of instability of the genetic construct for RNAi-silencing in genome of some transgenic plants; they show close correlation of the floury endosperm type and high in vitro protein digestibility.