Global gene expression analysis of pigeonpea with male sterility conditioned by A2 cytoplasm.

Abhishek Bohra,Dibendu Datta,Gandam Prasad,Lekha Pazhamala,Shalini Pareek,Rintu Jha,Rachit K Saxena,Rajeev K Varshney,Mohd Akram,Satheesh Naik Sj,Narendra P Singh,Abhishek Rathore,Khela Ram Soren,Abha Tiwari,Alok Kumar Maurya,Gaurav Pandey

doi:10.1002/tpg2.20132

Abstract

Cytoplasmic male sterility(CMS), a maternally inherited trait, provides a promising means to harness yield gains associated with hybrid vigor. In pigeonpea [Cajanus cajan (L.) Huth], nine types of sterility-inducing cytoplasm have been reported, of which A2 and A4 have been successfully deployed in hybrid breeding. Unfortunately, molecular mechanism of the CMS trait is poorly understood because of limited research invested. More recently, an association between a mitochondrial gene (nad7) and A4 -CMS has been demonstrated in pigeonpea; however, the mechanism underlying A2 -CMS still remains obscure. The current investigation aimed to analyze the differences in A2 -CMS line (ICPL 88039A) and its isogenic maintainer line (ICPL 88039B) at transcriptome level using next-generation sequencing. Gene expression profiling uncovered a set of 505 genes that showed altered expression in response to CMS, of which, 412 genes were upregulated while 93 were downregulated in the fertile maintainer line vs. the CMS line. Further, gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein-protein interaction (PPI) network analyses revealed association of CMS in pigeonpea with four major pathways: glucose and lipid metabolism, ATP production, pollen development and pollen tube growth, and reactive oxygen species (ROS) scavenging. Patterns of digital gene expression were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) of six candidate genes. This study elucidates candidate genes and metabolic pathways having potential associations with pollen development and male sterility in pigeonpea A2 -CMS. New insights on molecular mechanism of CMS trait in pigeonpea will be helpful to accelerate heterosis utilization for enhancing productivity gains in pigeonpea.

Highlights

Male sterility systems that circumvent the need of manual emasculation has given a great impetus to crop improvement in agricultural industry via exploitation of hybrid vigour (Dong et al, 2012)
To obtain genes responsible for cytoplasmic male sterility (CMS) induction in ICPL 88039A, total RNA was isolated from CMS line and cognate fertile line (ICPL 88039B) for the generation of cDNA library
We noticed enhanced expression for the genes that are related to cell wall loosening, such as polygalactouronase, expansins, pectate lyase, beta 1–3 glucosidase, endoglucanase, which is in accordance with the findings reported earlier by Rhee et al (2015) based on differential gene expression between the sterile line and its near isogenic fertile line

Summary

Introduction

Male sterility systems that circumvent the need of manual emasculation has given a great impetus to crop improvement in agricultural industry via exploitation of hybrid vigour (Dong et al, 2012). In pigeonpea [Cajanus cajan (L.) Huth], two types of male sterility systems were discovered: genic male sterility (GMS) and cytoplasmic male sterility (CMS). CMS became popular with the increasing availability of stable male sterile lines, a robust fertility restoration system, and a notable (up to 47%) yield advantage over the check varieties (Saxena et al, 2013). Availability of male sterility in plants contributes toward ensuring the seed purity that otherwise remains extremely difficult to achieve through manual emasculation (Liu et al, 2013). Two cytoplasms, A2 and A4 derived from C. scarabaeoides (L.) Thouars and C. cajanifolius (Haines) Maesen, respectively, have been successfully deployed for development of high-yielding hybrids (Bohra et al, 2020)

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