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The aromatic amino acids phenylalanine, tyrosine, and tryptophan in plants are not only essential components of protein synthesis, but also serve as precursorsfor a wide range of secondary metabolites and plant hormone, such as auxin, salicylicacid, lignin, and anthocyanin. These derivatives are very important for plant growth, and resistance to various biotic and abiotic stresses. Up to 30% of the carbon from photosynthesis is used to synthesize aromatic-derived metabolites. The aromatic amino acids are synthesized via the shikimate pathway in plastid. However,the function and regulation mechanism of several genes in this pathways are still unclear. Our previous work found a mutant (raa) with reduced aromatic amino acid synthesis and growth development defects in Arabidopsis thaliana. Using forward genetic screening, we have obtained a few mutants exhibited normal growth phenotype as the wild type. Further work will focus on the gene characterization by genome sequencing and functional analysis to identify new genes involved in the synthesis and regulation of aromatic amino acids in Arabidopsis.  Plant artificial chromosomes (PAC) is being used as a new vector to introduce chromosome segments into plant cell. We use PAC to introduce specific secondary metabolic pathways of higher plants into lower plants, such as Physcomitrella patens, to study the role of specific metabolites in plant evolution. Lignin is a phenylpropanoid-derived polymer that functions as a major component of cell wall peculiar to higher plants. Lower plants, such as bryophytes, do not have the ability to synthesize lignin. We use artificial chromosome technology to synthesize all genes involved in lignin biosynthesis and regulation, and transfer them into the P.patens to study whether the lignin biosynthesis can accelerate the evolution of plant height in bryophytes.  Phenylpropanoids are a diverse group of compounds derived from aromaticamino acid phenylalanine that are involved in plant defense, structuralsupport, plant development and so on. The phenylpropanoid pathway serves as arich source of secondary metabolites in plants, serving as a starting point forthe production of many important compounds, such as the lignin, flavonoids,coumarins and lignans. We use Arabidopsis as model system to elucidatemolecular details of the phenylpropanoid pathway. By using functional genomicsapproach, we have identified genes encoding proteins involved in biosynthesis,modification and regulation in the phenylpropanoid pathway.  |