Cinnamic acid (CA) is a natural compound and exists in both dicots and monocots. It serves as the precursor for biosynthesis of phenylpropanoids in plants. It has been reported that a UV-light activated cinnamic acid isomer (cis-CA) is able to regulate plant growth. Such an effect is both auxin and ethylene-independent.

To elucidate the molecular mechanisms underlying cis-CA-regulated plant growth, differential proteomics and forward genetic methods have been applied. A cis-CA-inducible gene (ZCE1) has been found. A genetic screening for Arabidopsis mutants resistant to cis-CA were also performed using root growth inhibition assay. Four Arabidopsis mutants, named cpar (c̲i̲s̲-p̲henylpropanoid a̲cid-r̲esponse) 1, 2, 3 and 4 were successfully isolated. All cpar mutants showed larger se...[ Read more ]

Cinnamic acid (CA) is a natural compound and exists in both dicots and monocots. It serves as the precursor for biosynthesis of phenylpropanoids in plants. It has been reported that a UV-light activated cinnamic acid isomer (cis-CA) is able to regulate plant growth. Such an effect is both auxin and ethylene-independent.

To elucidate the molecular mechanisms underlying cis-CA-regulated plant growth, differential proteomics and forward genetic methods have been applied. A cis-CA-inducible gene (ZCE1) has been found. A genetic screening for Arabidopsis mutants resistant to cis-CA were also performed using root growth inhibition assay. Four Arabidopsis mutants, named cpar (c̲i̲s̲-p̲henylpropanoid a̲cid-r̲esponse) 1, 2, 3 and 4 were successfully isolated. All cpar mutants showed larger seeds. Cpar1 also showed delayed senescence under CA treatment when grown in soil.

To further study the functions of these two genes in regulation of plant growth, promoter analysis has been employed. GUS reporter gene has been fused with these two promoters and transferred into the wild type Arabidopsis. Both GUS staining and assay have been performed to determine the promoter activity at various developmental stages or under different induction conditions. Our results show that ZCE1 has a basal expression throughout Arabidopsis adult plant, whereas CPAR1 gene is activated at the connection node, in both flower and silique. Cis-CA is able to induce ZCE1 gene expression in both etiolated and light-grown plants but not CPAR1. To find the cis-acting element within the cis-CA-inducible promoter of ZCE1, the -2.5 kb promoter of ZCE1 has been deleted in series from the 5' end upstream of the promoter region. The deletion of ZCE1 promoter shows that the resulting -0.5 kb (5F) promoter region upstream of transcription starting site has about 8 fold higher GUS activity than that of -2.5 kb long (1F) promoter in both dark and light grown seedlings, indicating that a cis-acting repressor may exist in between -2.0 to -0.5 kb promoter region. The -0.5 kb (5F) promoter region of ZCE1 is still able to respond to cis-CA induction. Thus, promoter analysis of this 0.5 kb region may reveal a novel cis-acting element specifically responsive to cis-CA induction in Arabidopsis.