Molecular characterization and functional analysis of CzR1, a coiled-coil-nucleotide-binding-site-leucine-rich repeat R-gene from Curcuma zedoaria Loeb. that confers resistance to Pythium aphanidermatum

• CzR1, a major R-gene was isolated from Curcuma zedoaria using RACE-PCR strategy.
• Structural analyses classified CzR1 as a non-TIR-CC-NBS-LRR R-gene.
• RT-PCR revealed specific expression of CzR1 only in pathogen resistant plant types.
• CzR1 shows upregulation in response to different strains of Pythium aphanidermatum.
• CzR1 shows highest transcript accumulation in the rhizome tissues of C. zedoaria.

Rhizome rot disease caused by necrotrophic oomycete Pythium aphanidermatum is responsible for upto 60% of yield losses in turmeric (Curcuma longa L). However, Curcuma zedoaria L, a wild relative of turmeric, is resistant to P. aphanidermatum and has been proposed as a potential donor for rot resistance to C. longa. We used a previously isolated resistance gene candidate Czp11 from C. zedoaria as a template to characterize a major resistance gene CzR1 through candidate gene approach in combination with RACE-PCR strategy. CzR1 encodes a 906 amino acid predicted protein with a calculated pI of 8.55. Structural and phylogenetic analyses grouped CzR1 within the non-TIR (homology to Toll/interleukin-1 receptors) subclass of NBS-LRR R-genes. Reverse transcription PCR revealed specific transcript expression of CzR1 only in P. aphanidermatum resistant lines of C. zedoaria and Zingiber zerumbet, another resistant wild species of the family Zingiberaceae. Semi quantitative RT-PCR analysis showed constitutive expression of CzR1 which gets significantly upregulated in response to infection by different strains of P. aphanidermatum. Although, the expression of CzR1 was reported in the root, leaf and rhizome tissues of C. zedoaria, the relative transcript expression was highest in the rhizomes. Elucidation of these molecular characteristics of CzR1 will pave way towards a broad spectrum rhizome rot resistance development in the cultivated turmeric.