Combined metabolome and transcriptome reveal HmF6'H1 regulating simple coumarin accumulation against powdery mildew infection in Heracleum moellendorffii Hance.

BACKGROUND: Powdery mildew, caused by Eeysiphe heraclei, seriously threatens Heracleum moellendorffii Hance. Plant secondary metabolites are essential to many activities and are necessary for defense against biotic stress. In order to clarify the functions of these metabolites in response to the pathogen, our work concentrated on the variations in the accumulation of secondary metabolites in H. moellendorffii during E. heraclei infection. RESULTS: Following E. heraclei infection, a significant upregulation of coumarin metabolites-particularly simple coumarins and associated genes was detected by RNA-seq and UPLC-MS/MS association analysis. Identifying HmF6'H1, a Feruloyl CoA 6'-hydroxylase pivotal in the biosynthesis of the coumarin basic skeleton through ortho-hydroxylation, was a significant outcome. The cytoplasmic HmF6'H1 protein was shown to be able to catalyze the ortho-hydroxylation of p-coumaroyl-CoA and caffeoyl-CoA, resulting in the formation of umbelliferone and esculetin, respectively. Over-expression of the HmF6'H1 gene resulted in increased levels of simple coumarins, inhibiting the biosynthesis of furanocoumarins and pyranocoumarins by suppressing PT gene expression, enhancing H. moellendorffii resistance to powdery mildew. CONCLUSIONS: These results established HmF6'H1 as a resistance gene aiding H. moellendorffii in combatting E. heraclei infection, offering additional evidence of feruloyl-CoA 6'-hydroxylase role in catalyzing various types of simple coumarins. Therefore, this work contributes to our understanding of the function of simple coumarins in plants' defense against powdery mildew infection.

Three-dimensional memristive Morris-Lecar model with magnetic induction effects and its FPGA implementation.

To characterize the magnetic induction flow induced by neuron membrane potential, a three-dimensional (3D) memristive Morris-Lecar (ML) neuron model is proposed in this paper. It is achieved using a memristor induction current to replace the slow modulation current in the existing 3D ML neuron model with fast-slow structure. The magnetic induction effects on firing activities are explained by the spiking/bursting firings with period-adding bifurcation and periodic/chaotic spiking-bursting patterns, and the bifurcation mechanisms of the bursting patterns are elaborated using the fast-slow analysis method to create two bifurcation sets. In particular, the 3D memristive ML model can also exhibit the homogeneous coexisting bursting patterns when switching the memristor initial states, which are effectively illustrated by the theoretical analysis and numerical simulations. Finally, a digitally FPGA-based hardware platform is developed for the 3D memristive ML model and the experimentally measured results well verify the numerical ones.

Morphological and physiological responses of Dianthus spiculifolius high wax mutant to low-temperature stress.

Cuticular wax plays a role in plant responses to environmental stresses. To understand the contribution of cuticular wax to plant responses to low-temperature stress, the morphological and physiological responses of a Dianthus spiculifolius high-wax (HW) mutant and wild type (WT) were compared. Under low-temperature stress (0 and -10 °C), HW plants showed a lower mortality rate and electrolyte leakage (El) than that WT plants. In plants treated with low-temperature stress (0 and -10 °C), HW mutant leaves exhibited higher soluble sugar and free proline contents and lower malondialdehyde contents than those WT leaves. The photosynthetic capacity, net photosynthetic rate, stomatal conductance, and maximal photochemical efficiency of photosystem II in HW mutant leaves were the least inhibited by low temperature than those in WT leaves. The dewaxing experiments showed no significant difference in the phenotype and El between the dewaxed-treated HW mutant and WT leaves under low-temperatures stress, indicating that cuticular wax causes differences in resistance to low-temperatures between HW and WT. Principal component analysis and the membership function value of the physiological data showed that the average membership value of the HW mutant was greater than that in WT. In general, the results indicated that high cuticular wax contributes positively to the response to low-temperature stress by D. spiculifolius.

Effects of shading on triterpene saponin accumulation and related gene expression of Aralia elata (Miq.) Seem.

Aralia elata (Miq.) Seem is widely used as a medicinal plant and functional food in China. In this study, A. elata plants were exposed to full sunlight (CK), 40% shading (LS), 60% shading (MS), and >80% shading (ES) condition to investigate the effects of shading treatments on growth, stress levels, antioxidant enzymes activity, araloside content and related gene expression. The greatest growth and leaf biomass were achieved in 40% shading, and leaf biomass per plant increased by 16.09% compared to the non-shading treatment. Furthermore, the lowest reactive oxide species (ROS) production and lipid peroxidation resulting from increasing antioxidant enzyme activity were also observed in LS treatment. Overall, shading percentage negatively regulated the expression of key enzymes (squalene synthase, SS; squalene epoxidase, SE and ß-amyrin synthase, bAS) involved in the saponin biosynthesis, resulting in the greatest yields of total and four selected aralosides in A. elata leaves were achieved in sunlight group. However, the greatest yield of total saponin in the leaves was observed in the 40% shading group due to higher leaf biomass. The results suggest that optimizing the field growing conditions would be important for obtaining the greatest yield of bioactive components. Total saponin and selected aralosides also have a significant correlation with ROS production and antioxidant enzyme activity, these indicated the increased yield of these saponins may be part of a defense response. The study concludes that the production of saponin was the interaction of oxidative stress and photosynthesis.

Identification and analysis of CYP450 and UGT supergene family members from the transcriptome of Aralia elata (Miq.) seem reveal candidate genes for triterpenoid saponin biosynthesis.

BACKGROUND: Members of the cytochrome P450 (CYP450) and UDP-glycosyltransferase (UGT) gene superfamily have been shown to play essential roles in regulating secondary metabolite biosynthesis. However, the systematic identification of CYP450s and UGTs has not been reported in Aralia elata (Miq.) Seem, a highly valued medicinal plant. RESULTS: In the present study, we conducted the RNA-sequencing (RNA-seq) analysis of the leaves, stems, and roots of A. elata, yielding 66,713 total unigenes. Following annotation and KEGG pathway analysis, we were able to identify 64 unigenes related to triterpenoid skeleton biosynthesis, 254 CYP450s and 122 UGTs, respectively. A total of 150 CYP450s and 92 UGTs encoding > 300 amino acid proteins were utilized for phylogenetic and tissue-specific expression analyses. This allowed us to cluster 150 CYP450s into 9 clans and 40 families, and then these CYP450 proteins were further grouped into two primary branches: A-type (53%) and non-A-type (47%). A phylogenetic analysis of 92 UGTs and other plant UGTs led to clustering into 16 groups (A-P). We further assessed the expression patterns of these CYP450 and UGT genes across A. elata tissues, with 23 CYP450 and 16 UGT members being selected for qRT-PCR validation, respectively. From these data, we identified CYP716A295 and CYP716A296 as the candidate genes most likely to be associated with oleanolic acid synthesis, while CYP72A763 and CYP72A776 were identified as being the most likely to play roles in hederagenin biosynthesis. We also selected five unigenes as the best candidates for oleanolic acid 3-O-glucosyltransferase. Finally, we assessed the subcellular localization of three CYP450 proteins within Arabidopsis protoplasts, highlighting the fact that they localize to the endoplasmic reticulum. CONCLUSIONS: This study presents a systematic analysis of the CYP450 and UGT gene family in A. elata and provides a foundation for further functional characterization of these two multigene families.

[Stimulatory effects of low temperature treatment of germinating seeds on flower-bud differentiation in broccoli].

The effects of low temperature treatment (0-2 degrees C) of germinating seeds in accelerating process of flower-bud differentiation in broccoli (Brassica oleracea var. italica) were studied. The results indicated that low temperature treatment of germinating seeds for 10 d in broccoli (T(10)) lowered 0.86 nodes and advanced 5 d for the critical stage of flower-bud differentiation, stage of primary furcation scape primordium differentiation and stage of secondary and tertiary furcation scape primordium differentiation; Low temperature treatment of germinating seeds for 20 d in broccoli (T(20)) lowered 1.03 nodes and advanced 6 d for the critical stage of flower-bud differentiation , stage of primary furcation scape primordium differentiation and stage of secondary and tertiary furcation scape primordium differentiation. The node number at which flower-bud differentiation started under T(10) and T(20) was significantly lower than that of control while there was no significant difference between T(10) and T(20). In addition, the flower-bud differentiation was accompanied by increase in GA(3) contents, soluble protein contents, POD activities and invertase activities. GA(3) contents, soluble protein contents, POD activities and invertase activities started to increase significantly when plants entered the critical stage of flower-bud differentiation; POD activities, invertase activities and GA(3) contents emerge high apex value when plants entered stage of primary furcation scape primordium differentiation and stage of secondary and tertiary furcation scape primordium differentiation. Curve change trend of these physiological and biochemical indexes under T(10) and T(20) were accord with CK while advent of each high apex value was earlier about a week than CK during flower-bud differentiation. In a word, synthesization of GA(3) was induced firstly after germinating seeds were treated under low temperature, consequently POD activities and invertase activities were increased which took advantage of flower-bud differentiation.