Transcriptional Response of Defensive and Regulatory Genes Involved in Tomato Plant Hormone Signaling Pathways against Fusarium Wilt

Fusarium wilt caused by the fungus Fusarium oxysporum f. sp. lycopersici (FOL) is one of the major devastating diseases of tomato plants throughout the world. There is no information on the molecular response of tomato line, Early Urbana-Y to FOL. The present study was performed to study the line response to FOL using phytopathological (disease severity and shoot fresh weight) as well as molecular methodologies. The transcription of several genes responsive to jasmonic acid (JA; Pin2), salicylic acid (SA; Chi3, Chi9 and PR1), the regulatory genes responsive to the signaling hormone JA (MYC2 and WRKY33) and ethylene (ET; ERF1) were studied by qRT-PCR technique at different time points after FOL inoculation (6-96 hour after inoculation). Disease symptoms development and reduced shoot fresh weight of the inoculated plants despite up-regulation of SA-dependent defense genes at different time points after pathogen infection indicated that SA signaling pathway is involved in the susceptibility of the Early Urbana-Y line to FOL. In contrast, JA and ET pathway genes were not strongly induced in response to the pathogen suggesting the involvement of JA/ET-mediated defense responses in reducing disease susceptibility. However, to gain a better understanding of enhanced resistance to fusarium wilt, more detailed molecular mechanisms underlying susceptibility of Early Urbana-Y line to FOL need to be further investigated in the future.