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Expression analysis of fertilization/early embryogenesis-associated genes in Phalaenopsis orchids.

ABSTRACT: One of the distinct reproductive programs in orchid species is pollination-triggered ovule development and megasporogenesis. During sexual reproduction, fertilization occurs days to months after pollination. The molecular mechanisms evolved to carry out this strategic reproductive program remain unclear. In the August issue of Plant Physiology 1 , we report comprehensive studies of comparative genome-wide gene expression in various reproductive tissues and the molecular events associated with developmental transitions unique to sexual reproduction of Phalaenopsis aphrodite. Transcriptional factors and signaling components whose expression is specifically enriched in interior ovary tissues when fertilization occurs and embryos start to develop have been identified. Here, we report verification of additional fertilization-associated genes, DOMAINS REARRANGED METHYLTRANSFERASE 1 (PaDRM1), CHROMOMETHYLTRANSFERASE 1 (PaCMT1), SU(VAR)3-9 RELATED PROTEIN 1 (PaSUVR1), INDOLE-3-ACETIC ACID inducible 30-like 1 (PaIAA30L1), and ETHYLENE INSENSITIVE 3-like 1 (PaEIN3L1), and discuss their potential roles in gametophyte development, epigenetic reprogramming, and hormone regulation during fertilization and establishment of embryo development in Phalaenopsis orchids.

SUBMITTER: Chen JC

PROVIDER: S-EPMC5117094 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Expression analysis of fertilization/early embryogenesis-associated genes in Phalaenopsis orchids.

Chen Jhun-Chen JC Wei Miao-Ju MJ Fang Su-Chiung SC

Plant signaling & behavior 20161001 10

One of the distinct reproductive programs in orchid species is pollination-triggered ovule development and megasporogenesis. During sexual reproduction, fertilization occurs days to months after pollination. The molecular mechanisms evolved to carry out this strategic reproductive program remain unclear. In the August issue of Plant Physiology <sup>1</sup> , we report comprehensive studies of comparative genome-wide gene expression in various reproductive tissues and the molecular events associa ...[more]

PMID: 27668884

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Project description:BACKGROUND:Phalaenopsis represents an important cash crop worldwide. Abundant flower colors observed in Phalaenopsis orchids range from red-purple, purple, purple-violet, violet, and violet-blue. However, violet-blue orchids are less bred than are those of other colors. Anthocyanin, vacuolar pH and metal ions are three major factors influencing flower color. This study aimed to identify the factors causing the violet-blue color in Phalaenopsis flowers and to analyze whether delphinidin accumulation and blue pigmentation formation can be achieved by transient overexpression of heterologous F3'5'H in Phalaenopsis. RESULTS:Cyanidin-based anthocyanin was highly accumulated in Phalaenopsis flowers with red-purple, purple, purple-violet, and violet to violet-blue color, but no true-blue color and no delphinidin was detected. Concomitantly, the expression of PeF3'H (Phalaenopsis equestrsis) was high, but that of PhF3'5'H (Phalaenopsis hybrid) was low or absent in various-colored Phalaenopsis flowers. Transient overexpression of DgF3'5'H (Delphinium grandiflorum) and PeMYB2 in a white Phalaenopsis cultivar resulted a 53.6% delphinidin accumulation and a novel blue color formation. In contrast, transient overexpression of both PhF3'5'H and PeMYB2 did not lead to delphinidin accumulation. Sequence analysis showed that the substrate recognition site 6 (SRS6) of PhF3'5'H was consistently different from DgF3'5'Hs at positions 5, 8 and 10. Prediction of molecular docking of the substrates showed a contrary binding direction of aromatic rings (B-ring) with the SRS6 domain of DgF3'5'H and PhF3'5'H. In addition, the pH values of violet-blue and purple Phalaenopsis flowers ranged from 5.33 to 5.54 and 4.77 to 5.04, respectively. Furthermore, the molar ratio of metal ions (including Al3+, Ca2+ and Fe3+) to anthocyanin in violet-blue color Phalaenopsis was 190-, 49-, and 51-fold higher, respectively, than those in purple-color Phalaenopsis. CONCLUSION:Cyanidin-based anthocyanin was detected in violet-blue color Phalaenopsis and was concomitant with a high pH value and high molar ratio of Al3+, Ca2+ and Fe3+ to anthocyanin content. Enhanced expression of delphinidin is needed to produce true-blue Phalaenopsis.

Project description:BACKGROUND:Transposable elements (TEs) are fragments of DNA that can insert into new chromosomal locations. They represent a great proportion of eukaryotic genomes. The identification and characterization of TEs facilitates understanding the transpositional activity of TEs with their effects on the orchid genome structure. RESULTS:We combined the draft whole-genome sequences of Phalaenopsis equestris with BAC end sequences, Roche 454, and Illumina/Solexa, and identified long terminal repeat (LTR) retrotransposons in these genome sequences by using LTRfinder and classified by using Gepard software. Among the 10 families Gypsy-like retrotransposons, three families Gypsy1, Gypsy2, and Gypsy3, contained the most copies among these predicted elements. In addition, six high-copy retrotransposons were identified according to their reads in the sequenced raw data. The 12-kb Orchid-rt1 contains 18,000 copies representing 220 Mbp of the P. equestris genome. Southern blot and slot blot assays showed that these four retrotransposons Gypsy1, Gypsy2, Gypsy3, and Orchid-rt1 contained high copies in the large-genome-size/large-chromosome species P. violacea and P. bellina. Both Orchid-rt1 and Gypsy1 displayed various ratios of copy number for the LTR sequences versus coding sequences among four Phalaenopsis species, including P. violacea and P. bellina and small-genome-size/small-chromosome P. equestris and P. ahprodite subsp. formosana, which suggests that Orchid-rt1 and Gypsy1 have been through various mutations and homologous recombination events. FISH results showed amplification of Orchid-rt1 in the euchromatin regions among the four Phalaenopsis species. The expression levels of Peq018599 encoding copper transporter 1 is highly upregulated with the insertion of Orchid-rt1, while it is down regulated for Peq009948 and Peq014239 encoding for a 26S proteasome non-ATP regulatory subunit 4 homolog and auxin-responsive factor AUX/IAA-related. In addition, insertion of Orchid-rt1 in these three genes are all in their intron regions. CONCLUSION:Orchid-rt1 and Gypsy1-3 have amplified within Phalaenopsis orchids concomitant with the expanded genome sizes, and Orchid-rt1 and Gypsy1 may have gone through various mutations and homologous recombination events. Insertion of Orchid-rt1 is in the introns and affects gene expression levels.

Project description:Background: The early stages of D. melanogaster embryogenesis involve cell migration and pattern formation, and lead to the formation of three germ layers (the ectoderm, mesoderm and endoderm). These developmental events are controlled by differential gene activity. In the current study we used a suppressive subtractive hybridization (SSH) procedure to identify a group of genes potentially involved in D. melanogaster early embryogenesis and to study the temporal activity of developmentally regulated genes at five different intervals covering 12 stages of embryogenesis. Results: Macroarrays were constructed to confirm induction of expression and determine the temporal profile of isolated subtracted cDNAs during embryo development. We identified a set of 118 genes that significantly increased their expression levels at least at one developmental interval compared with the reference interval. 53.4% of them have a phenotype and/or molecular function reported in the literature, whereas 46.6% are essentially uncharacterized. Clustering analysis revealed demarcated transcript groups with maximum gene activity at distinct developmental intervals. In situ hybridization assays were carried out on 30 of the transcripts and of these, 19 (63%) proved to have restricted expression patterns. 11 of the uncharacterized genes that exhibited temporal and spatially restricted patterns of expression in developing embryos encode putative secreted and transmembrane proteins. For three of them we validated our protein sequence predictions by expressing their cDNAs in S2R+ cells and analyze the subcellular distribution of recombinant proteins. Conclusions: Our data provides a list of developmentally regulated D. melanogaster genes and their expression profiles during embryogenesis, including novel information on the temporal and spatial expression patterns of several previously uncharacterized genes. In particular, we recovered a significant number of novel genes encoding putative secreted and transmembrane proteins, suggesting new components of signalling pathways that might be incorporated within the existing regulatory networks controlling Drosophila embryogenesis; they are also good candidates for more functional targeted analyses. Keywords: Drosophila melanogaster, gastrulation, macroarray, developmental time course We generated a subtracted stage specific cDNA library representing genes differentially expressed between Drosophila melanogaster synciyial blastoderm and gastrula stages. Clones were spotted onto nylon membranes and hybridized against cDNA probes representing mRNA from embryos at five different developmental intervals, in order to obtain time course expression data covering the first 12 stages of Drosophila development. We designed macroarrays containing either 302 non-redundant cDNAs, including protein-coding sequences, ncRNA, transposons, introns and intergenic regions (membranes A, B and C) and the complete subtracted library (579 cDNAs, membrane D). Each clone was spotted in duplicate. The following controls were spotted onto membranes: (1) a fragment of the vector pBluescript II obtained by amplification with the T7 and SP6 universal primers; (2) several spots of DMSO 50% (solvent used); (3) PCR amplified fragment of genes serendipity Î±, twist, tinman, fog and snail as positive controls, and (4) actin, tubulin, and RP49 as housekeeping, and (5) four dilutions of a PCR amplified fragment from a B. subtilis dap cDNA (ATCC; number 87486), which hybridizes to an in vitro synthesized poly(A)-RNA that was added to the embryo RNA samples (dilution 1/200) prior to the labelling process and used as spike mRNA (Kane et al., 2000).

Dataset Information

Expression analysis of fertilization/early embryogenesis-associated genes in Phalaenopsis orchids.

Publications

Expression analysis of fertilization/early embryogenesis-associated genes in Phalaenopsis orchids.

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