Genotype-independent Agrobacterium rhizogenes-mediated root transformation of chickpea: a rapid and efficient method for reverse genetics studies

Abstract

Background: Chickpea (Cicer arietinum L.), an important legume crop is one of the major source of dietary protein. Developing an efcient and reproducible transformation method is imperative to expedite functional genomics studies in this crop. Here, we present an optimized and detailed procedure for Agrobacterium rhizogenes-mediated root transformation of chickpea. Results: Transformation positive roots were obtained on selection medium after two weeks of A. rhizogenes inoculation. Expression of green fuorescent protein further confrmed the success of transformation. We demonstrate that our method adequately transforms chickpea roots at early developmental stage with high efciency. In addition, root transformation was found to be genotype-independent and the efcacy of our protocol was highest in two (Annigiri and JG-62) of the seven tested chickpea genotypes. Next, we present the functional analysis of chickpea hairy roots by expressing Arabidopsis TRANSPARENT TESTA 2 (AtTT2) gene involved in proanthocyanidins biosynthesis. Overexpression of AtTT2 enhanced the level of proanthocyanidins in hairy roots that led to the decreased colonization of fungal pathogen, Fusarium oxysporum. Furthermore, the induction of transgenic roots does not afect functional studies involving infection of roots by fungal pathogen. Conclusions: Transgenic roots expressing genes of interest will be useful in downstream functional characterization using reverse genetics studies. It requires 1 day to perform the root transformation protocol described in this study and the roots expressing transgene can be maintained for 3–4 weeks, providing sufcient time for further functional studies. Overall, the current methodology will greatly facilitate the functional genomics analyses of candidate genes in root-rhizosphere interaction in this recalcitrant but economically important legume crop.