Leaf anatomy micromorphometry plasticity and histochemistry of Azadirachta indica during acclimatization

Abstract Environmental conditions of grow can modify leaf structure and metabolite production. Neem plants produce a high amount of medicinal metabolites and contain biopesticide terpenoids with low toxicity. However, the high genetic variation and the low material quality, besides the environmental modifications warn to the need of biotechnological techniques to ensure the production of high quality metabolites. The aim was to investigate leaf structural and histochemical characteristics of Azadirachta indica grown in vitro, in vivo and acclimatized condition. It was found anatomical differences among the environments, with higher leaf thickness associated to in vivo conditions, as well as were more evenly distributed stomata. Those modifications did not qualitatively affect the production of medicinal metabolites and biopesticides. Terpenes and tannins were observed in specialized cells called idioblasts, located in the mesophyll and in the midrib region, respectively. Thus, in a qualitative approach, we can affirm that the different environments do not modify metabolites production. Increased production of these bioactive compounds could be achieved by isolation and in vitro culture of idioblasts as a new source of research in plant biotechnology.

Salinity-induced modifications on growth, physiology and 20-hydroxyecdysone levels in Brazilian-ginseng [Pfaffia glomerata (Spreng.) Pedersen]

- Salinity is a major threat to agriculture. However, depending on the concentration of soluble salts in soil, increased secondary metabolite levels can occur with no major damages to plant growth and development. The phytoecdysteroid (PE) 20-hydroxyecdysone (20E) is a secondary metabolite with biotechnological, medicinal, pharmaceutical and agrochemical applicability. Here, we characterize the responses (growth and physiology) of Pfaffia glomerata under different NaCl concentrations and examine the production of 20E as affected by salinity. Forty-day-old plants grown in greenhouse were exposed to 0, 120, 240, 360 or 480 mM of NaCl for 11 days. Moderate salinity (i.e., 120 mM of NaCl) led to increased 20E concentrations in leaves (47%) relative to the control with no significant effect on photosynthesis and biomass accumulation, thus allowing improved 20E contents on a per whole-plant basis. In contrast, plants under high salinity (i.e., 240-480 mM of NaCl) displayed similar 20E concentrations in leaves compared to the control, but with marked impairments to biomass accumulation and photosynthetic performance (coupled with decreased sucrose and starch levels) in parallel to nutritional imbalance. High salinity also strongly increased salicylic acid levels, antioxidant enzyme activities, and osmoregulatory status. Regardless of stress severity, 20E production was accompanied by the upregulation of Spook and Phantom genes. Our findings suggest that P. glomerata cultivation in moderate salinity soils can be considered as a suitable agricultural option to increase 20E levels, since metabolic and structural complexity that makes its artificial synthesis very difficult.

De novo assembly and transcriptome of Pfaffia glomerata uncovers the role of photoautotrophy and the P450 family genes in 20-hydroxyecdysone production

Pfaffia glomerata is a medically important species because it produces the phytoecdysteroid 20-hydroxyecdysone (20-E). However, there has been no ready-to-use transcriptome data available in the literature for this plant. Here, we present de novo transcriptome sequencing of RNA from P. glomerata in order to investigate the 20-E production as well as to understand the biochemical pathway of secondary metabolites in this non-model species. We then analyze the effect of photoautotrophy on the production of 20-E genes phylogenetically identified followed by expression analysis. For this, total messenger RNA (mRNA) from leaves, stems, roots, and flowers was used to construct indexed mRNA libraries. Based on the similarity searches against plant non-redundant protein database, gene ontology, and eukaryotic orthologous groups, 164,439 transcripts were annotated. In addition, the effect of photoautotrophy in two genes putatively involved in the 20-E synthesis pathway was analyzed. The Phantom gene (CYP76C), a precursor of the route, showed increased expression in P. glomerata plants cultured under photoautotrophic conditions. This was accompanied by increased production of this metabolite indicating a putative involvement in 20-E synthesis. This work reveals that several genes in the P. glomerata transcriptome are related to secondary metabolism and stresses, that genes of the P450 family participate in the 20-E biosynthesis route, and that plants cultured under photoautotrophic conditions promote an upregulated Phantom gene and enhance the productivity of 20-E. The data will be used for future investigations of the 20-E synthesis pathway in P. glomerata while offering a better understanding of the metabolism of the species.

Coupling physiological analysis with proteomic profile to understand the photosynthetic responses of young Euterpe oleracea palms to drought

This study examined whether drought sensitivity in açaí (Euterpe oleracea Mart.) is associated with reductions in photosynthesis and increasing oxidative stress in response to down-regulation of proteins related to photosynthetic reactions, photorespiration, and antioxidant system. Well-watered (Control) and drought-stressed plants were compared when leaf water potential in stressed plants reached around - 1.5 and - 3.0 MPa, representing moderate and severe drought. Drought caused 84 and 96% decreases in net photosynthetic rate (P_n) and stomatal conductance. Stress-mediated changes in maximum quantum efficiency of photosystem II (PSII) photochemistry were unobserved, but drought decreased photochemical quenching, actual quantum yield of PSII electron transport, and apparent electron transport rate (ETR). Moderate and severe drought induced, respectively, decreases and increases in non-photochemical quenching (NPQ) and 74 and 273% increases in ETR/P_n. Moderate drought down-regulated PSII protein D2, chlorophyll a-b binding protein 8, photosystem I reaction center subunit N, sedoheptulose-1,7-bisphosphatase, and transketolase; while severe drought down-regulated LHC II proteins, ferredoxin-NADP reductase, ATP synthase subunits ε and ß, and carbonic anhydrase isoform X2. The glutamate-glyoxylate aminotransferase 2 and glycine dehydrogenase were down-regulated upon moderate drought, while catalase 2 and glycine cleavage system H protein 3 were up-regulated. Severe drought up-regulated glycolate oxidase, glycine cleavage system H protein 3, and aminomethyl transferase, but most of photorespiration-related proteins were only found in control plants. Down-regulation of chaperones and antioxidant enzymes and increased lipid peroxidation in stressed plants were observed upon both stress severities. Therefore, the decreases in P_n and failure in preventing oxidative damages through adjustments in NPQ and photorespiration- and antioxidant-related proteins accounted for drought sensitivity in açaí.

Expression of Cyp6g1 and Cyp12d1 in DDT resistant and susceptible strains of Drosophila melanogaster

The Rst(2)DDT locus (loci) in Drosophila is associated with the over-expression of two cytochrome P450 genes, Cyp6g1 and Cyp12d1. Using northern and western blot analysis we observed the expression pattern of these two genes in two DDT susceptible (Canton-S and 91-C) and three DDT resistant strains (Wisconsin, 91-R and Hikone-R). In Canton-S and 91-R, the CYP6G1 protein was constitutively expressed throughout development. In the Wisconsin strain, CYP6G1 was not expressed in third instar larvae unless the larvae are exposed to DDT. CYP12D1 protein was only expressed in adults. Cyp12d1 mRNA is induced in DDT resistant strains post-exposure to DDT and the expression patterns of Cyp12d1 mRNA varied across DDT resistant strains. Our data support the hypothesis that there is evolutionary plasticity in the expression patterns of P450s associated with metabolic pesticide resistance.