Identification and functional analysis of ZmDLS associated with the response to biotic stress in maize.

Terpenes are the main class of secondary metabolites produced in response to pest and germ attacks. In maize (Zea mays L.), they are the essential components of the herbivore-induced plant volatile mixture, which functioned as a direct or indirect defense against pest and germ attacks. In this study, 43 maize terpene synthase gene (ZmTPS) family members were systematically identified and analyzed through the whole genomes of maize. Nine genes, including Zm00001d032230, Zm00001d045054, Zm00001d024486, Zm00001d004279, Zm00001d002351, Zm00001d002350, Zm00001d053916, Zm00001d015053, and Zm00001d015054, were isolated for their differential expression pattern in leaves after corn borer (Ostrinia nubilalis) bite. Additionally, six genes (Zm00001d045054, Zm00001d024486, Zm00001d002351, Zm00001d002350, Zm00001d015053, and Zm00001d015054) were significantly upregulated in response to corn borer bite. Among them, Zm00001d045054 was cloned. Heterologous expression and enzyme activity assays revealed that Zm00001d045054 functioned as d-limonene synthase. It was renamed ZmDLS. Further analysis demonstrated that its expression was upregulated in response to corn borer bites and Fusarium graminearum attacks. The mutant of ZmDLS downregulated the expressions of Zm00001d024486, Zm00001d002351, Zm00001d002350, Zm00001d015053, and Zm00001d015054. It was more attractive to corn borer bites and more susceptible to F. graminearum infection. The yeast one-hybrid assay and dual-luciferase assay showed that ZmMYB76 and ZmMYB101 could upregulate the expression of ZmDLS by binding to the promoter region. This study may provide a theoretical basis for the functional analysis and transcriptional regulation of terpene synthase genes in crops.

Weighted gene co-expression network analysis reveals key module and hub genes associated with the anthocyanin biosynthesis in maize pericarp.

Anthocyanins are the visual pigments that present most of the colors in plants. Its biosynthesis requires the coordinated expression of structural genes and regulatory genes. Pericarps are the rich sources of anthocyanins in maize seeds. In the experiment, the transcriptomes of transparent and anthocyanins-enriched pericarps at 15, 20, and 25 DAP were obtained. The results output 110.007 million raw reads and 51407 genes' expression matrix. Using data filtration in R language, 2057 genes were eventually identified for weighted gene co-expression network analysis. The results showed that 2057 genes were classified into ten modules. The cyan module containing 183 genes was confirmed to be the key module with the highest correlation value of 0.98 to the anthocyanins trait. Among 183 genes, seven structural genes were mapped the flavonoid biosynthesis pathway, and a transcription factor Lc gene was annotated as an anthocyanin regulatory gene. Cluster heatmap and gene network analysis further demonstrated that Naringenin, 2-oxoglutarate 3-dioxygenase (Zm00001d001960), Dihydroflavonol 4-reductase (Zm00001d044122), Leucoanthocyanidin dioxygenase (Zm00001d014914), anthocyanin regulatory Lc gene (Zm00001d026147), and Chalcone synthase C2 (Zm00001d052673) participated in the anthocyanins biosynthesis. And the transcription factor anthocyanin regulatory Lc gene Zm00001d026147 may act on the genes Chalcone synthase C2 (Zm00001d052673) and Dihydroflavonol 4-reductase (Zm00001d044122). The yeast one-hybrid assays confirmed that the Lc protein could combine with the promoter region of C2 and directly regulate the anthocyanin biosynthesis in the pericarp. These results may provide a new sight to uncover the module and hub genes related to anthocyanins biosynthesis in plants.

Dynamic Transcriptome-Based Weighted Gene Co-expression Network Analysis Reveals Key Modules and Hub Genes Associated With the Structure and Nutrient Formation of Endosperm for Wax Corn.

The endosperm of corn kernel consists of two components, a horny endosperm, and a floury endosperm. In the experiment, a kind of floury endosperm corn was identified. The result of phenotypic trait analysis and determination of amino acid content showed that the floury endosperm filled with the small, loose, and scattered irregular spherical shape starch granules and contained higher content of amino acid. The starch biochemical properties are similar between floury corns and regular flint corn. By using dynamically comparative transcriptome analysis of endosperm at 20, 25, and 30 DAP, a total of 113.42 million raw reads and 50.508 thousand genes were obtained. By using the weighted gene co-expression network analysis, 806 genes and six modules were identified. And the turquoise module with 459 genes was proved to be the key module closely related to the floury endosperm formation. Nine zein genes in turquoise module, including two zein-alpha A20 (Zm00001d019155 and Zm00001d019156), two zein-alpha A30 (Zm00001d048849 and Zm00001d048850), one 50 kDa gamma-zein (Zm00001d020591), one 22 kDa alpha-zein 14 (Zm00001d048817), one zein-alpha 19D1 (Zm00001d030855), one zein-alpha 19B1 (Zm00001d048848), and one FLOURY 2 (Zm00001d048808) were identified closely related the floury endosperm formation. Both zein-alpha 19B1 (Zm00001d048848) and zein-alpha A30 (Zm00001d048850) function as source genes with the highest expression level in floury endosperm. These results may provide the supplementary molecular mechanism of structure and nutrient formation for the floury endosperm of maize.

Systematic analysis of MYB gene family in Acer rubrum and functional characterization of ArMYB89 in regulating anthocyanin biosynthesis.

The v-myb avian myeloblastosis viral oncogene homolog (MYB) family of transcription factors is extensively distributed across the plant kingdom. However, the functional significance of red maple (Acer rubrum) MYB transcription factors remains unclear. Our research identified 393 MYB transcription factors in the Acer rubrum genome, and these ArMYB members were unevenly distributed across 34 chromosomes. Among them, R2R3 was the primary MYB sub-class, which was further divided into 21 sub-groups with their Arabidopsis homologs. The evolution of the ArMYB family was also investigated, with the results revealing several R2R3-MYB sub-groups with expanded membership in woody species. Here, we report on the isolation and characterization of ArMYB89 in red maple. Quantitative real-time PCR analysis revealed that ArMYB89 expression was significantly up-regulated in red leaves in contrast to green leaves. Sub-cellular localization experiments indicated that ArMYB89 was localized in the nucleus. Further experiments revealed that ArMYB89 could interact with ArSGT1 in vitro and in vivo. Overexpression of ArMYB89 in tobacco enhances the anthocyanin content of transgenic plants. In conclusion, our results contribute to the elucidation of a theoretical basis for the ArMYB gene family, and provide a foundation for further characterization of the biological roles of MYB genes in the regulation of Acer rubrum leaf color.

Comparative transcriptome analysis of differentially expressed genes related to the physiological changes of yellow-green leaf mutant of maize.

Chlorophylls, green pigments in chloroplasts, are essential for photosynthesis. Reduction in chlorophyll content may result in retarded growth, dwarfism, and sterility. In this study, a yellow-green leaf mutant of maize, indicative of abnormity in chlorophyll content, was identified. The physiological parameters of this mutant were measured. Next, global gene expression of this mutant was determined using transcriptome analysis and compared to that of wild-type maize plants. The yellow-green leaf mutant of maize was found to contain lower contents of chlorophyll a, chlorophyll b and carotenoid compounds. It contained fewer active PSII centers and displayed lower values of original chlorophyll fluorescence parameters than the wild-type plants. The real-time fluorescence yield, the electron transport rate, and the net photosynthetic rate of the mutant plants showed reduction as well. In contrast, the maximum photochemical quantum yield of PSII of the mutant plants was similar to that of the wild-type plants. Comparative transcriptome analysis of the mutant plants and wild-type plants led to the identification of differentially expressed 1,122 genes, of which 536 genes were up-regulated and 586 genes down-regulated in the mutant. Five genes in the chlorophyll metabolism pathway, nine genes in the tricarboxylic acid cycle and seven genes related to the conversion of sucrose to starch displayed down-regulated expression. In contrast, genes encoding a photosystem II reaction center PsbP family protein and the PGR5-like protein 1A (PGRL1A) exhibited increased transcript abundance.

Functional analysis of ZmMADS1a reveals its role in regulating starch biosynthesis in maize endosperm.

MADS-box family proteins play an important role in grain formation and flower development; however, the molecular mechanisms by which transcription factors regulate the starch metabolism pathway are unclear in maize. Here, we report a transcription factor, ZmMADS1a, that controls starch biosynthesis in maize (Zea mays L.). We demonstrate the expression of ZmMADS1a in tassel, silk, and endosperm, and show that the protein is localized to the cell nucleus. Compared with the control, seeds of overexpressing ZmMADS1a increased starch content (especially amylose content), had smaller starch granules and altered chemical structure. Meanwhile, overexpression of ZmMADS1a resulted in increases in the contents of soluble sugars and reducing sugars in maize. ZmMADS1a plays a positive regulatory role in the starch biosynthesis pathway by up-regulating several starch biosynthesis related genes. We also show that ZmMADS1a has a similar adjustment mechanism of starch biosynthesis in rice. Collectively, our study suggests that ZmMADS1a functions as a positive regulator of starch biosynthesis by regulating the expression of key starch metabolism genes during seed development.

Comparative transcriptome analysis reveals differentially expressed genes related to the tissue-specific accumulation of anthocyanins in pericarp and aleurone layer for maize.

Purple corn is a rich source of anthocyanins. In the experiment, two anthocyanins-enriched purple corn lines Ha0414 and Ha6130 were identified. The anthocyanins were respectively accumulated in the pericarp of Ha0414 and the aleurone layer of Ha6130 with different composition and content. Transcriptome analysis of the two tissues in both lines identified 16 and 14 differentially expressed genes belonging to anthocyanin metabolism pathway in pericarp and the aleurone layer, individually. Of these genes, two genes encoding 2-oxoglutarate (2OG) and Fe (II)-dependent oxygenase superfamily proteins, and one gene annotated as UDP-glycosyltransferase superfamily protein exhibited increased transcript abundance in both the colored pericarp and aleurone layer. Otherwise, one gene annotated as flavonoid 3', 5'-hydroxylase, and another gene encoding flavonoid 3'-monooxygenase displayed increased transcript abundance in the aleurone layer of Ha6130. Moreover, 36 transcription factors were identified with increased transcript abundance in the pericarp of Ha0414, such as bHLH transcription factors, WRKY transcription factors, and HB transcription factors. And 79 transcription factors were isolated with an increased expression level in the aleurone layer of Ha6130, including MYB transcription factors, MYB-related transcription factors, and bHLH transcription factors. These genes expression may result in the tissue-specific accumulation of anthocyanins in pericarp and aleurone layer.

[Studies on genetic diversity of medicinal Dendrobium by SRAP].

OBJECTIVE: To study the genetic diversity of medicinal Dendrobium by SRAP. METHOD: The genetic diversity of 9 spices Dendrobium was studied by using the optimized SRAP reaction system. The NTSYS software was used to analyze the markers. RESULT: Forty primer pairs were selected from 88 amplified 1 782 polymorphic bands with an average of 44.55 polymorphic bands per primer pair. Cluster analysis using UPGMA method based on the data of SRAP amplified bands by 40 primer pairs showed that 9 spices of could be distinguished into two main groups. Jaccard's similarity coefficient ranged from 0.330 2-0.789 2. CONCLUSION: The results of this research indicate that SRAP molecular marker is efficient to study the medical Dendrobium genetic diversity.