Wheat WCBP1 encodes a putative copper-binding protein involved in stripe rust resistance and inhibition of leaf senescence
Senescence is a highly regulated developmental process that has some overlap with response to pathogen stress. Many senescence-associated genes (SAGs) play an important role in pathogenic fungi defence, although their exact function remains unclear. We previously identified a stripe rust pathogen-induced up-regulated EST (EL773044) from the suppression subtractive hybridisation (SSH)-cDNA library of wheat cultivar Shaanmai 139 that was induced by Puccinia striiformis West (Pst) race CYR 32. To further understand the role of SAGs in wheat defence, a wheat SAG orthologue was identified and characterised, and was named TaSAG 120 (GenBank: JN558557). The cDNA consisted of 1040 nucleotides and contained an open reading frame of 384 nucleotides encoding a polypeptide of 127 amino acids. The estimated molecular weight was 14.1 kDa with a pI of 9.56. A hydrophobic region was observed at positions 56–75 in the amino acid sequence. Using DNA from nulli-tetrasomic lines and polymerase chain reaction (PCR) primers based on related Triticum sequences, PCR results showed that TaSAG 120 is a multi-copy gene without introns. Transcriptome analysis indicated that TaSAG 120 was involved in plant defence against Puccinia striiformis West infection. However, TaSAG expression in immune incompatible interactions was lower than that in the compatible interactions 1–3 days post-inoculation with Pst CYR 32 in hexaploid wheat. This implied that TaSAG is a negative indicator linked to the level or capacity of plant defences against pathogen infection. Fluctuations in the extent of TaSAG expression as a result of pathogen challenge in immune resistant wheat may play a crucial role in translating the induced modulations into a pathogen-defence response.