Changes of phenolic compounds in LebZIP2-overexpressing transgenic plants

The bZIP gene is a transcription factor that plays various roles in relation to plant stress and hormone signaling. This gene is also involved in plant environmental stress and herbicide tolerance. We generated Nicotiana benthamiana transgenic plants with LebZIP2-encoding gene isolated from tomatoes using Agrobacterium-mediated transformation. Transgenic seeds harvested from these T0 transgenic plants were grown and examined for gene transfer and changes in phenolic compounds in the T1 generation. RT-PCR analysis using a primer specific to the LebZIP gene confirmed that the gene was transferred to the T1 generation. We analyzed the increase and decrease tendency for 30 phenolic compounds using the T1 generation-transgenic plants and investigated the mechanism between the specifically increased compound and LebZIP2 gene. Gallic acid, homogentisic acid, protocatechuic acid, myricetin, t-cinnamic acid, and b-resorcyclic acid were identified as the phenolic compounds that increased in T1 transgenic plants overexpressing the LebZIP gene. Among these, homogentisic acid at 246.75-1055.19 µg/g, was increased by 2-5 fold in the T1 transgenic plants compared to the control. Protocatechuic acid was found at 1640.54-2456.00 µg/g and was increased by 2-4 fold in T1 transgenic plants. t-Cinnamic acid was present in a small amount of 23.14 µg/g in the control, whereas it was 102.19-135.47 µg/g in T1 transgenic plants, showing an increase of 4-5 folds. These results indicated that homogentisic acid, protocatechuic acid, and t-cinnamic acid among the 30 phenolic compounds analyzed, were significantly increased in LebZIP2-overexpressing T1 transgenic plants, and support the evidence that the LebZIP2 gene is significantly involved in the increment of three phenolic compounds.