Over-Expression of a Transcription Factor Gene BoC3H4 Enhances Salt Stress Tolerance but Reduces Sclerotinia Stem Rot Disease Resistance in Broccoli

C3H-type zinc finger genes play diverse roles in plant growth, development, and stress responses. In our present study, a C3H-type gene namely BoC3H4 was isolated from broccoli. BoC3H4 was 1629 bp in length encoding 542 amino acid residues. The deduced protein sequence contained two ankyrin repeats and two CCCH zinc finger motifs, and those motifs shared high identities with homologous sequences from other Cruciferae plants. The expression levels of BoC3H4 elevated when subjected to both salt stress and Sclerotinia sclerotiorum infection. Broccoli plants with constitutive expression of BoC3H4 demonstrated increased tolerance toward salinity stress, accompanied by a prominent accumulation of proline, and a remarkable decrease of chlorophyll loss, MDA, REC, as well as H2O2 accumulation compared to WT plants. Moreover, over-expression of BoC3H4 in broccoli lines decreased resistance to S. sclerotiorum, and it could not induce the expression of BoPDF1.2 gene, the marker gene for JA/ET signaling pathway. Our study proposes that BoC3H4 acts as a positive regulator of plant tolerance to salinity stress and a negative regulator of resistance to necrotrophic pathogen S. sclerotiorum.