In vivo analysis of plant promoters and transcription factors by agroinfiltration of tobacco leaves

A convenient, Agrobacterium-mediated transient expression assay has been ev aluated for rapid analysis of plant promoters and transcription factors in vivo. By simple infiltration of Agrobacterium cells carrying appropriate pl asmid constructs into tobacco leaves in planta, reproducible expression ass ays could be conducted in as little as 2-3 days without using expensive equ ipment (e.g. biolistic gun or electroporation apparatus) or complicated pro cedures (e.g. preparation of protoplasts). Biotic and abiotic treatments co uld be applied to the intact plant to examine their influence on promoter a ctivity and gene expression. Using this method, we have tested the stress-r esponsive as-1 and heat shock elements, yeast GAL4 transactivation system, two promoters of pathogenesis-related (PR) genes as well as a heat shock pr omoter. Through deletion analyses of tobacco PR1a promoter and a novel myb1 promoter, we have also successfully identified the cis-regulatory regions in these promoters that are responsive to salicylic acid treatment or tobac co mosaic virus infection. Together, our results demonstrate that Agrobacte rium-mediated transient expression is a simple and efficient method for in vivo assays of plant promoters and transcription factors.