<italic>TaPP2-A13</italic> gene shows induced expression pattern in wheat responses to stresses and interacts with adaptor protein SKP1 from SCF complex

To explore the function and molecular mechanism of Phloem protein 2 (PP2) gene in wheat (Triticum aestivum L.) response to stresses, a TaPP2-A13 putatively encoding a PP2 protein was obtained from TcLr15, a wheat near isogenic line against leaf rust pathogen, in the present study. The complete coding region of TaPP2-A13 encodes a hydrophilic polypeptide with molecular weight of 33.18 kD, and theoretical isoelectric point is 6.36. There is an F-box domain at N-terminal and a PP2 domain at C-terminal of the TaPP2-A13 protein sequence, which indicates that wheat TaPP2-A13 belongs to F-box/PP2 (FBP) subfamily. Wheat TaPP2-A13 shared relatively higher sequence similarity with PP2-A13 from Gramineae. Quantitative real-time PCR (qRT-PCR) results indicated that TaPP2-A13 was induced by infection of leaf rust pathogen (Puccinia triticina), and showed stronger expression in susceptible combination than that in resistant one. An obvious up-regulation of TaPP2-A13 was observed after treatment with abscisic acid (ABA), salicylic acid (SA) and methyl jasmonate (MeJA) in wheat. TaPP2-A13 was significantly down-regulated after treatment with PEG and H₂O₂, while TaPP2-A13 striking increased first, then fell down after NaCl treatment in wheat. Subcellular localization result indicated that TaPP2-A13 distributed in both of the nucleus and cytoplasm. The recombinant vector BD-TaPP2-A13 was used as the bait to screen Yeast 2 Hybrid (Y2H) library, 11 kinds of proteins were finally obtained. Further Y2H assays identified that TaPP2-A13 physically interacted with five kinds of proteins including TaPP2C5, TaSLY1, TaCHI, TaRbcS, and TaSKP1. BiFC and Co-IP results further confirmed that TaPP2-A13 interacted with TaSKP1, an adaptor protein from SKP1-Cullin-F-box (SCF) complex, which made us to speculate that TaPP2-A13 functions as a member of SCF complex by binding with TaSKP1. These findings laid some foundation for further analyzing the function of TaPP2-A13 and exploring its regulatory network.