Molecular characterization of a gene encoding a vegetative storage protein (CiVSP) from Cichorium intybus and its expression in the root and shoot in relation to nitrogen status and pathogen resistance

In addition to their putative role in nitrogen storage, some vegetative storage proteins (VSPs) support further roles in biotic and abiotic stress responses. Functions of the 17 kDa VSP from witloof chicory (CiVSP) in N storage and plant resistance to pathogens and its regulation by nitrogen were investigated. The N‐terminal end of this protein was sequenced and the corresponding full‐length cDNA was obtained. The expression of the CiVsp gene was studied in various organs of chicory grown under replete or limited nitrogen supply. A strong expression of CiVsp was observed in both taproot and fine roots of mature plants and seedlings. CiVsp transcripts were also detected in mature leaves, especially in veins. In senescing leaves CiVsp transcripts accumulated concomitantly to a decrease in RbcS transcript abundance and Rubisco small‐subunit degradation. CiVSP protein accumulated significantly only in the subterranean part of the plant during late stages of development. Nitrate limitation caused a reduction in CiVsp mRNA accumulation and a delay in CiVSP storage in the taproot. It is concluded that CiVSP accumulation is regulated at the transcriptional level by N external supply and that the protein is involved in long and short‐term N storage. In silico analysis indicated that CiVSP is highly homologous with several allergens and PR‐10 proteins. Moreover, CiVsp transcript and protein expression were significantly higher in Erwinia carotovora‐resistant chicory inbred lines compared with susceptible lines, suggesting its involvement in chicory resistance to pathogens attack.