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Sporopollenin Monomer Biosynthesis in Arabidopsis
김성수,Carl J. Douglas 한국식물학회 2013 Journal of Plant Biology Vol.56 No.1
Land plants have evolved aliphatic biopolymersthat protect their cell surfaces against dehydration, pathogens,and chemical and physical damage. In flowering plants, acritical event during pollen maturation is the formation of thepollen surface structure. The pollen wall consists essentiallyof the microspore-derived intine and the sporophyte-derivedexine. The major component of the exine is termedsporopollenin, a complex biopolymer. The chemical compositionof sporopollenin remains poorlycharacterized because it isextremely resistant to chemical and biological degradationprocedures. Recent characterization of Arabidopsis thalianagenes and corresponding enzymes involved in exineformation has demonstrated that the sporopollenin polymerconsists of phenolic and fatty acid-derived constituents thatare covalently coupled by ether and ester linkages. Thisreview illuminates the outlines of a biosynthetic pathwayinvolved in generating monomer constituents of thesporopollenin biopolymer component of the pollen wall.
Shanda Liu,Xiaoping Wang,Eryang Li,Carl J. Douglas,Jin-Gui Chen,Shucai Wang 한국식물학회 2013 Journal of Plant Biology Vol.56 No.4
R2R3 MYB transcription factors regulate multiple aspects of plant growth and development. Here we report the identification of PtrMYB192, a Populus R2R3 MYB transcription factor, as a negative regulator of flowering time. By using quantitative RT-PCR, we found that PtrMYB192, but not its closely homologous gene PtrMYB028, is highly expressed in mature leaves in Populus. Heterologously expression of PtrMYB192 under control of 35S promoter in Arabidopsis resulted in late flowering phenotypes under both long and short day conditions, indicating that PtrMYB192 controls flowering time independent of the photoperiod pathway. Domain swapping experiment showed that neither PtrMYB028DB-192AD nor PtrMYB192DB-028AD affected flowering time when heterologously expressed in Arabidopsis. However, when recruit to the promoter of a GAL4-GUS reporter gene by a GAL4 DNA binding domain in Arabidopsis protoplasts, both of PtrMYB028DB-192AD and PtrMYB192DB-028AD activated the reporter gene. Quantitative RT-PCR results showed an elevated expression of the floral repressor gene FLOWERING LOCUS C (FLC), but not the flowering-promoting gene CONSTANS (CO) in PtrMYB192 transgenic plants. Taken together, these results suggest that PtrMYB192 is a transcription activator that negatively regulating flowering time in Arabidopsis by activating FLC and possible other genes, and that both R2R3 DNA binding domain and activation domain maybe required for its full function.
Wei Wang,Eryang Li,Ilga Porth,Jin-Gui Chen,Shawn D. Mansfield,Carl J. Douglas,Shucai Wang 한국식물학회 2016 Journal of Plant Biology Vol.59 No.1
Among the R2R3 MYB transcription factors that involve in the regulation of secondary cell wall formation in Arabidopsis, MYB46 alone is sufficient to induce the entire secondary cell wall biosynthesis program. PtrMYB021, the poplar homolog of MYB46, has been reported to regulate secondary cell wall formation when expressed in Arabidopsis. We report here that spatially and temporally restricted expression of PtrMYB021 is critical for its function in regulating secondary cell wall formation. By using quantitative RT-PCR, we found that PtrMYB021 was expressed primarily in xylem tissues. When expressed in Arabidopsis under the control of PtrCesA8, but not the 35S promoter, PtrMYB021 increased secondary cell wall thickness, which is likely caused by increased lignification as well as changes in cell wall carbohydrate composition. In consistent with this, elevated expression of lignin and cellulose biosynthetic genes were observed in the transgenic plants. When expressed in Arabidopsis protoplasts as fusion proteins to the Gal4 DNA binding domain, PtrMYB021 activated the reporter gene Gal4-GUS. In summary, our results suggest that PtrMYB021 is a transcriptional activator, and spatially and temporally restricted expression of PtrMYB021 in Arabidopsis regulates secondary cell wall formation by activating a subset of secondary cell wall biosynthesis genes.