Vol.:(0123456789) 1 3 Plant Molecular Biology https://doi.org/10.1007/s11103-019-00899-7 Comparative transcriptome analyses provide novel insights into the diferential response of Pigeonpea (Cajanus cajan L.) and its wild relative (Cajanus platycarpus (Benth.) Maesen) to herbivory by Helicoverpa armigera (Hübner) Maniraj Rathinam 1  · Pragya Mishra 1  · Ajay Kumar Mahato 1  · Nagendra Kumar Singh 1  · Uma Rao 2  · Rohini Sreevathsa 1 Received: 8 April 2019 / Accepted: 26 June 2019 © Springer Nature B.V. 2019 Key message Deeper insights into the resistance response of Cajanus platycarpus were obtained based on comparative transcriptomics under Helicoverpa armigera infestation. Abstract Devastation by pod borer, Helicoverpa armigera is one of the major factors for stagnated productivity in Pigeon- pea. Despite possessing a multitude of desirable traits including pod borer resistance, wild relatives of Cajanus spp. have remained under-utilized due to linkage drag and cross-incompatibility. Discovery and deployment of genes from them can provide means to tackle key pests like H. armigera. Transcriptomic diferences between Cajanus platycarpus and Cajanus cajan during diferent time points (0, 18, 38, 96 h) of pod borer infestation were elucidated in this study. For the frst ever time, we demonstrated captivating variations in their response; C. platycarpus apparently being reasonably agile with efectual transcriptomic reprogramming to deter the insect. Deeper insights into the diferential response were obtained by identifcation of signifcant GO-terms related to herbivory followed by combined KEGG and ontology analyses. C. platycar- pus portrayed a multilevel response with cardinal involvement of SAR, redox homeostasis and reconfguration of primary metabolites leading to a comprehensive defense response. The credibility of RNA-seq analyses was ascertained by transient expression of selected putative insect resistance genes from C. platycarpus viz., chitinase (CHI4), Alpha-amylase/subtilisin inhibitor (IAAS) and Flavonoid 3_5 hydroxylase (C75A1) in Nicotiana benthamiana followed by efcacy analysis against H. armigera. qPCR validated results of the study provided innovative insights and useful leads for development of durable pod borer resistance. Keywords Helicoverpa armigera · Pigeonpea wild relatives · Insect resistance · RNA seq · Cajanus spp. Introduction Pigeonpea (Cajanus cajan (L.) Millsp) is one of the most important legume crops of India belonging to the genus Cajanus and family Fabaceae. This legume is an integral component of the livelihood of marginal resource poor farm- ers apart from being a key source of dietary protein for the vegetarian population (Rani et al. 2018). Though pigeonpea has always occupied an important place as a food legume with continued eforts towards crop improvement, stagnant and unstable productivity are the characteristic features of this crop due to its inability to alleviate various biotic and abiotic factors (Choudhary et al. 2013). Among the biotic stress factors, insect pests pose intense threat to plants and are responsible for substantial yield losses either by direct Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11103-019-00899-7) contains supplementary material, which is available to authorized users. * Uma Rao umanema@gmail.com * Rohini Sreevathsa rohinisreevathsa@gmail.com 1 ICAR-National Institute for Plant Biotechnology, Pusa Campus, New Delhi, India 2 Division of Nematology, ICAR-Indian Agricultural Research Institute, Pusa, New Delhi, India