Transient expression assays
For ProPAL1:GUS vector construction, an approximately 2000-bp promoter fragment of PAL1 was amplified by gene-specific primers (Table S1) and cloned into the pCAMBIA-1301 vector. To generatePro35S:WRKY75 , the WRKY75 cDNA fragment was amplified and inserted into the pCAMBIA-1301 vector. The 35S:PtrWRKY75construct was used as an effector. Leaves of N. benthamiana were infiltrated with A. tumefaciens cells containing the effector and reporter using the agroinfiltration method (Yang et al. , 2000). Activity of GUS was measured using a previously described method (Jefferson et al., 1987), which monitored the cleavage of the β-glucuronidase substrate 4-methylumbelliferyl β-D-glucuronide by hydrolysis to produce the fluorescent 4-methylumbelliferone. Protein concentrations were measured as described by Bradford (1976).