Genome-scale analyses of polyketide synthases in banana: Phylogenetics and expression profiling forecast their candidacy in specialized metabolism

A chromosome-scale genome assembly of turmeric provides insights into curcumin biosynthesis and tuber formation mechanism

Curcuma longa, known as the 'golden spice' and 'life spice', is one of the most commonly utilized spices in the world and also has medicinal, cosmetic, dye and flavoring values. Herein, we present the chromosomal-level genome for turmeric to explore the differences between tubers and rhizomes in the regulation of curcumin biosynthesis and the mechanism of tuber formation. We assembled the turmeric genome into 21 pseudochromosomes using Pacbio long reads complemented with Hi-C technologies, which has a total length of 1.11 Gb with scaffold N50 of 50.12 Mb and contains 49,612 protein-coding genes. Genomic evolutionary analysis indicated that turmeric and ginger have shared a recent WGD event. Contraction analysis of gene families showed possible roles for transcription factors, phytohormone signaling, and plant-pathogen interactions associated genes in adaptation to harsh environments. Transcriptomic data from tubers at different developmental stages indicated that candidate genes related to phytohormone signaling and carbohydrate metabolic responses may be associated with the induction of tuber formation. The difference in curcumin content between rhizomes and tubers reflected the remodeling of secondary metabolites under environmental stress, which was associated with plant defense in response to abiotic stresses. Overall, the availability of the C. longa genome provides insight into tuber formation and curcumin biosynthesis in turmeric as well as facilitating the understanding of other Curcuma species.

Polyketide synthases (PKSs) of secondary metabolism: in silico identification and characterization in orchids

Type III polyketide synthases (PKSs) catalyse the formation of an array of polyketides with diverse structures that play an important role in secondary metabolism in plants. This group of enzymes is encoded by a multigene family, the Type III polyketide synthase (PKS) gene family. Vast reserves of secondary metabolites in orchids make these plants suitable candidates for research in the area. In this study, genome-wide searches lead to the identification of five PeqPKS, eight DcaPKS and six AshPKS genes in Phalaenopsis equestris, Dendrobium catenatum and Apostasia shenzhenica, respectively. All the members showed the presence of two characteristic conserved domains (Chal_sti_synt_N and Chal_sti_synt_C) and were generally localised in the cytoplasm. The phylogenetic analysis led to the classification of these proteins into two groups: CHS (chalcone synthase (CHS) and non-CHS. A single protein in P. equestris and two proteins each in D. catenatum and A. shenzhenica clustered within the CHS clade. The majority of the genes exhibited similar structural patterns with a single intron. Expression profiling revealed the tissue-specific expression of these genes with high expression in reproductive tissues for most genes. A number of stress-responsive cis-regulatory elements were predicted, noteworthy amongst these are, ABRE and CGTCA that are chiefly responsible for responding to abscisic acid and methyl jasmonate, respectively. Our study provides a reference framework for future studies involving functional elucidation of PKS genes and biotechnological production of polyketides.Communicated by Ramaswamy H. Sarma.