ABSTRACT
Cinnamomum species attract attentions owing to their scents, medicinal properties, and ambiguous relationship in the phylogenetic tree. Here, we report a high-quality genome assembly of Cinnamomum camphora, based on which two whole-genome duplication (WGD) events were detected in the C. camphora genome: one was shared with Magnoliales, and the other was unique to Lauraceae. Phylogenetic analyses illustrated that Lauraceae species formed a compact sister clade to the eudicots. We then performed whole-genome resequencing on 24 Cinnamomum species native to China, and the results showed that the topology of Cinnamomum species was not entirely consistent with morphological classification. The rise and molecular basis of chemodiversity in Cinnamomum were also fascinating issues. In this study, six chemotypes were classified and six main terpenoids were identified as major contributors of chemodiversity in C. camphora by the principal component analysis. Through in vitro assays and subcellular localization analyses, we identified two key terpene synthase (TPS) genes (CcTPS16 and CcTPS54), the products of which were characterized to catalyze the biosynthesis of two uppermost volatiles (i.e. 1,8-cineole and (iso)nerolidol), respectively, and meditate the generation of two chemotypes by transcriptional regulation and compartmentalization. Additionally, the pathway of medium-chain triglyceride (MCT) biosynthesis in Lauraceae was investigated for the first time. Synteny analysis suggested that the divergent synthesis of MCT and long-chain triglyceride (LCT) in Lauraceae kernels was probably controlled by specific medium-chain fatty acyl-ACP thioesterase (FatB), type-B lysophosphatidic acid acyltransferase (type-B LPAAT), and diacylglycerol acyltransferase 2b (DGAT 2b) isoforms during co-evolution with retentions or deletions in the genome.
ABSTRACT
A laboratory test on the effects of differents simulated tide-inundated times with 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24 h x d(-1) on the growth of Avicennia marina seedlings was conducted. The ten growth information indices including chlorophyll, root vigor, growth, biomass and photosynthetic rate were mensurated. The principal components analysis was made combining the ten growth information indices. The 210 d experimental results showed that the chlorophyll, root vigor, growth and biomass would rise first and then fall as the extension of the inundate time; and they changed suddenly at the threshold inundate time 16 h x d(-1). The growth and biomass of Avicennia marina seedlings with more than 16 hours tide-inundated time per day were less than them with no more than 16 hours tide-inundated time per day. The maximum value of stem increment each month, leaf blade increment each month, dry weight of stem, dry weight of root and total biomass were under the 10 hours tide-inundated time per day. It concluded that Avicennia marina seedlings would grow adaptively with less than 16 hours tide-inundated time per day, 8-12 hours of tide-inundated time per day is the most suitable for the growth of Avicennia marina seedlings, while 16 h x d(-1) is a critical tide-inundated time when the plant responded to be obviously inadaptable.
