Seed-type vacuolar processing enzymes recognize the 619th asparagine residue to post translationally cleave the HMW-GS 1Dy10-m619SN allele

https://onlinelibrary.wiley.com/doi/10.1111/tpj.70697

Plant Journal, 2026 Jan; 125(2): e70697. doi: 10.1111/tpj.70697.

Yan Wang , Yang Li , Zhenru Guo, Qingcheng Li, Linlin Zhou, Xin Chen, Jie Deng, Xin Yuan, Lirun Chen, Qian Zha, Li Kong, Yongfang Wan, Malcolm J Hawkesford, Yunfeng Jiang, Yazhou Zhang, Qiang Xu, Qiantao Jiang, Jirui Wang, Guoyue Chen, Jian Ma, Youliang Zheng, Yuming Wei, Qing Chen, Pengfei Qi

Abstract

High molecular weight glutenin subunits (HMW-GSs) are critical grain storage proteins in wheat, which govern its unique processing quality. A HMW-GS 1Dy10 allele variant (1Dy10-m619SN), carrying a serine-to-asparagine substitution at the 619th residue, undergoes partial posttranslational cleavage. This modification leads to improved cookie-making quality. However, the enzymes mediating this cleavage remain unknown. In this study, we identified vacuolar processing enzymes (VPEs) as candidates for 1Dy10-m619SN processing using TurboID-based proximity labeling and RNA-seq analysis. In vitro cleavage assays confirmed that VPEs catalyzed 1Dy10-m619SN cleavage. Phylogenic analysis revealed that there are two seed-type VPEs in wheat, TaVPEI and TaVPEII, with TaVPEI being further subdivided into TaVPEI-1, TaVPEI-2, and TaVPEI-3. Despite sharing conserved catalytic domains, these isoforms display distinct temporal expression patterns, with TaVPEI-1 expression showing the strongest correlation with the posttranslational cleavage of 1Dy10-m619SN. TaVPEI-1 protein is localized to the vacuole, the well-known deposition site for HMW-GSs. Overexpression of TaVPEI-1 in wheat enhances the 1Dy10-m619SN cleavage. Collectively, these findings demonstrate that the seed-type VPEs in wheat are responsible for the posttranslational cleavage of 1Dy10-m619SN, which provides new insights into the molecular basis of wheat's unique processing quality.