| Flavonoids are polyphenolic secondary metabolites, widely existing in plant kingdom. They possess various bioactivities, such as antioxodant, anti-inflanmatory, anti-virus, and anti-aging being called "plant nutriments". Thus, flavonoids are becoming the hottest health-caring products and medicines. To investigate flavonoids biosynthesis at molecular level and provide new target genes for metabolic engineering of flavonoids biosynthesis pathway, the full-length cDNA of IbCHI of sweetpotato involved in the metabolic pathway of flavonoids was cloned by the RACE method, then characterized.CHI is an essential enzyme of the flavonoids biosynthesis pathway. The full-length cDNA of IbCHI was 780 bp containing a 732 bp open reading frame (ORF) encoding a polypeptide of 243 amino acids with a calculated molecular mass of 25.7 KDa and an isoelectric point of 5.167. Comparative and bioinformatic analyses revealed that IbCHI had extensive homology with CHIs from other species, especially had high similarities with CHIs from other plant species (60% identities). IbCHI contained Ile-42 and Lys-45 active sites that were considered as the highly conservative sites of catalytic region of CHIs. A phylogenetic tree of CHIs was constructed from different organisms including plants and algaes. The result demonstrated that CHIs were derived from an ancestor gene and evoluted into three groups, and IbCHI belonged to plant CHIs’ family. Furthermore, IbCHI had the closest genetic relationship with Eustoma grandiflorum and Petunia hybrida CHI. Tissue expression pattern analysis indicated that CHI expressed constitutively in all tissues including roots, stems, young leaves, old leaves and petiole with higher expression in young leaves. The cloning and characterization of IbCHI will be helpful to understand more about the role of CHI involved in the flavonoids biosynthesis at the molecular level.Sweetpotato (Ipomoea batatas (L.) Lam.) is a tuber-bearing species and represents an economically important crop in the world. The storage roots of sweetpotato contain a high amount of starch, which is as high as 30% of fresh weight for some cultivars. Sweetpotato can grow under a wide range of agroecological conditions. High male sterility, incompatibility and the hexaploid nature of sweetpotato have resulted in very limited improvement of this plant by classical breeding methods. Therefore, interest has been directed towards the genetic improvement of this crop through novel in vitro techniques, such as somatic hybridization, somaclonal variation and genetic transformation. One of the main difficulties is the control of plant regeneration, for which sweetpotato is considered a recalcitrant species. Among various systems of plant regeneration, somatic embryogenesis is highly desired, as the process regularly provides high multiplication rates and can effectively be maintained for a long time.Shoot tips of purple cultivar of sweetpotato were induced to form embryogenic callus in a culture medium solidified with Gelrite, and supplemented with 2mg·L-1 2,4-D. The cultivar gave an embryogenic response. Best results with an average of 85.71% embryogenic callus response were obtained with the medium. The plant conversion was dramatically improved by subculture of the embryogenic callus on the medium with the auxin of ABA alone before transfer of mature embryos. Further development into plants required the transfer of embryogenic callus onto hormone-free medium. |
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