Differential gene expression analyses of ten defence response genes during Fusarium wilt infection in resistant and susceptible pigeonpea cultivars

The present study was undertaken to partly understand the molecular mechanism of defence response during pigeonpea-Fusarium udum interaction. To study the response of defence related gene expression using reverse transcription quantitative real time PCR (RT-qPCR), roots of resistant and susceptible pigeonpea cultivars were infected with F. udum pathogen and samples were collected at 2, 24, 48, and 72 h after inoculation (HAI). PR2, PR10, PAL2, CHS8, IFS1, F3H, LOX, ADC, SPDS, and SPMS were amongst the ten defence response genes studied. The major changes observed in gene expression for all the ten genes are as follows: (i) Out of the ten genes, the expression of three genes, PR2, PR10, and CHS8, peaked at 48 HAI in resistant cultivars compared to susceptible cultivars (ii) the expression of two genes, IFS1 and F3H, was highly induced at all stages in resistant cultivars, while some genotypic differences were observed in susceptible cultivars (iii) the expression of the LOX gene increased only during the early stages at 2 HAI but decreased at later stages in resistant cultivars (iv) In resistant cultivars, the expression of three genes involved in polyamine synthesis, namely ADC, SPDS, and SPMS, peaked at 24 HAI compared to susceptible cultivars. Overall, increased gene expression was found mostly at earlier stages of infection, indicating that these genes are important in providing early resistance to F. udum infection in pigeon pea cultivars. The LOX gene, which codes for the lipooxygenase enzyme, appears to play a role in conferring susceptibility to pigeonea cultivars against F. udum infection, though more research is needed. Further validation studies of all ten genes using overexpression or RNAi technology will provide more information about their roles in the pigeonpea-F.udum interaction.