Cloning and expression of three PAL genes in Astragalus membranaceus / 中草药

ABSTRACT

Objective To disclose the molecular mechanism of calycosin-7-O-β-D-glucoside (CG) accumulation in Astragalus membranaceus, we cloned PAL genes and analyzed the expression patterns of them and changes of CG contents in different tissues of A. membranaceus. Methods PAL genes were cloned with the methods of homology cloning and RACE technique using the total RNA as template and the analysis of bioinformatics on the cloned genes was carried out, gene expressions in root, stem, and leaf were determined with real-time PCR method, and CG content in root, stem, and leaf were analyzed by HPLC methods. Results Three PAL genes were cloned from A. membranaceus. The genbank accession number was KY086279 (AmPAL1), KY086280 (AmPAL2), and KY086281 (AmPAL3), respectively; The full-length cDNA of them was 2 508 bp, 2 401 bp, and 2 498 bp, respectively; And they all consisted of 2 157 bp open reading frame encoding 718 amino acids. Deduced AmPAL proteins had typical active sequences of PAL proteins, they were homology with other PAL proteins, and they shared the highest identities with PAL proteins of leguminous plants. Phylogenetic tree analysis showed AmPAL1 belonged to the different sub-class with the sub-class of AmPAL2 and AmPAL3. Real-time PCR analysis indicated that expression levels of AmPALs were different from each other, the expression level of AmPAL1 was the highest, the expression level of AmPAL2 was the next, and that of AmPAL3 was lowest in all detected tissues, and only the expression levels of AmPAL2 was similar to the changes of CG contents in different tissues (root > stem > leaf). Conclusion The cloned AmPAL1, AmPAL2, and AmPAL3 from A. membranaceus were typical genes of PAL, each might have different function in developing of different tissues, and AmPAL2 might involve in CG accumulation in different tissues.