Integrated analysis of metabolome and transcriptome reveals key candidate genes involved in flavonoid biosynthesis in Pinellia ternata under heat stress.

Pinellia ternata (Thunb.) Breit. is an important traditional Chinese medicinal herb and very sensitive to high temperatures. To gain a better understanding of flavonoid biosynthesis under heat stress in P. ternata, we performed integrated analyses of metabolome and transcriptome data. P. ternata plants were subjected to a temperature of 38 °C, and samples were collected after 10 d of treatment. A total of 502 differential accumulated metabolites and 5040 different expressed transcripts were identified, with flavonoid biosynthesis predominantly enriched. Integrated metabolomics and transcriptome analysis showed that high temperature treatment upregulated the expression of CYP73A and downregulated the expression of other genes (such as HCT, CCoAOMT, DFR1, DFR2), which might inhibit the biosynthesis of the downstream metabolome, including such metabolites as chlorogenic acid, pelargonidin, cyanidin, and (-)-epigallocatechin in the flavonoid biosynthesis pathway. The transcription expression levels of these genes were validated by real-time PCR. Our results provide valuable insights into flavonoid composition and accumulation patterns and the candidate genes participating in the flavonoid biosynthesis pathways under heat stress in P. ternata.

Dipeptidase PEPDA Is Required for the Conidiation Pattern Shift in Metarhizium acridum.

Filamentous fungi conduct two types of conidiation, typical conidiation from mycelia and microcycle conidiation (MC). Fungal conidiation can shift between the two patterns, which involves a large number of genes in the regulation of this process. In this study, we investigated the role of a dipeptidase gene pepdA in conidiation pattern shift in Metarhizium acridum, which is upregulated in MC pattern compared to typical conidiation. Results showed that disruption of the pepdA resulted in a shift of conidiation pattern from MC to typical conidiation. Metabolomic analyses of amino acids showed that the levels of 19 amino acids significantly changed in ΔpepdA mutant. The defect of MC in ΔpepdA can be rescued when nonpolar amino acids, α-alanine, ß-alanine, or proline, were added into sucrose yeast extract agar (SYA) medium. Digital gene expression profiling analysis revealed that PEPDA mediated transcription of sets of genes which were involved in hyphal growth and development, sporulation, cell division, and amino acid metabolism. Our results demonstrated that PEPDA played important roles in the regulation of MC by manipulating the levels of amino acids in M. acridum. IMPORTANCE Conidia, as the asexual propagules in many fungi, are the start and end of the fungal life cycle. In entomopathogenic fungi, conidia are the infective form essential for their pathogenicity. Filamentous fungi conduct two types of conidiation, typical conidiation from mycelia and microcycle conidiation. The mechanisms of the shift between the two conidiation patterns remain to be elucidated. In this study, we demonstrated that the dipeptidase PEPDA, a key enzyme from the insect-pathogenic fungus Metarhizium acridum for the hydrolysis of dipeptides, is associated with a shift of conidiation pattern. The conidiation pattern of the ΔpepdA mutant was restored when supplemented with the nonpolar amino acids rather than polar amino acids. Therefore, this report highlights that the dipeptidase PEPDA regulates MC by manipulating the levels of amino acids in M. acridum.

Role of hunchback in segment patterning of Locusta migratoria manilensis revealed by parental RNAi.

In long germ embryos, all body segments are specified simultaneously during the blastoderm stage. In contrast, in short germ embryos, only the anterior segments are specified during the blastoderm stage, leaving the rest of the body plan to be specified later. The striking embryological differences between short and long germ segmentation imply fundamental differences in patterning at the molecular level. To gain insights into the segmentation mechanisms of short germ insects, we have investigated the role of the homologue of the Drosophila gap gene hunchback (hb) in a short germ insect Locusta migratoria manilensi by paternal RNA interference (RNAi). Phenotypes resulting from hb knockdown were categorized into three classes based on severity. In the most extreme case, embryos developed the most anterior structures only, including the labrum, antennae and eyes. The following conclusions were drawn: (i) L. migratoria manilensis hb (Lmm'hb) controls germ band morphogenesis and segmentation in the anterior region; (ii) Lmm'hb may function as a gap gene in a wide domain including the entire gnathum and thorax; and (iii) Lmm'hb is required for proper growth of the posterior germ band. These findings suggest a more extensive role for L. migratoria manilensis hunchback in anterior patterning than those described in Drosophila.