Degradation Mechanism and Chemical Component Changes in Betula platyphylla Wood by Wood-Rot Fungi

Cellulose synthase (CESA), which is an essential catalyst for the generation of plant cell wall biomass, is mainly encoded by the CesA gene family that contains ten or more members. In this study; four full-length cDNAs encoding CESA were isolated from Betula platyphylla Suk., which is an important timber species, using RT-PCR combined with the RACE method and were named as BplCesA3, −4, −7 and −8. These deduced CESAs contained the same typical domains and regions as their Arabidopsis homologs. The cDNA lengths differed among these four genes, as did the locations of the various protein domains inferred from the deduced amino acid sequences, which shared amino acid sequence identities ranging from only 63.8% to 70.5%. Real-time RT-PCR showed that all four BplCesAs were expressed at different levels in diverse tissues. Results indicated that BplCESA8 might be involved in secondary cell wall biosynthesis and floral development. BplCESA3 appeared in a unique expression pattern and was possibly involved in primary cell wall biosynthesis and seed development; it might also be related to the homogalacturonan synthesis. BplCESA7 and BplCESA4 may be related to the formation of a cellulose synthase complex and participate mainly in secondary cell wall biosynthesis. The extremely low expression abundance of the four BplCESAs in mature pollen suggested very little involvement of them in mature pollen formation in Betula. The distinct expression pattern of the four BplCesAs suggested they might participate in developments of various tissues and that they are possibly controlled by distinct mechanisms in Betula.

A crude oil-degrading bacterium named strain H9-3 was isolated from crude oil contaminated soil in the Northeastern area of China. Based on its morphological characteristics and 16S rDNA sequence analysis, strain H9-3 is affiliated to Acinetobacter pittii in the group of Gammaproteobacteria. The strain was efficient in removing 36.8% of the initial 10 g·L ${}^{-1}$ of crude oil within 21 days. GC-MS was performed and a preference was shown for n-C10, n-C11, i-C14, i-C17, i-C34, n-C12, n-C13, n-C14, n-C27, n-C32 and i-C13, over n-C16, n-C18–C22, n-C24–n-C31, and n-C36. This can be regarded as the specific fingerprint for crude oil degradation by strain H9-3 of Acinetobacter pittii. In addition to crude oil, it was shown that soybean oil and phenols can be utilized as carbon sources by strain H9-3. It was also shown that aniline and $\alpha$ -naphthol cannot be utilized for growth, but they can be tolerated by strain H9-3. Methylbenzene was neither utilized nor tolerated by strain H9-3. Although n-hexadecane was not preferentially consumed by strain H9-3, during culture with crude oil, it could be utilized for growth when it is the sole carbon source. The degradation of some branched alkanes (i-C14, i-C17 and i-C34) and the preferential degradation of crude oil over phenols could be used as a reference for distinguishing A. pittii from A. calcoaceticus. The difference in gene expression was very significant and was induced by diverse carbon sources, as shown in the qRT-PCR results. The oxidation and adhesion events occurred at high frequency during alkane degration by Acinetobacter pittii strain H9-3 cells.

Dynamic changes in callose content, which is deposited as a plant defense response to physiological changes, were analyzed during somatic embryogenesis in Eleutherococcus senticosus zygotic embryos plasmolyzed in 1.0 M mannitol. During plasmolysis, callose deposition was clearly observed inside the plasma membrane of zygotic embryo epidermal cells using confocal laser scanning microscopy. The callose content of zygotic embryos gradually increased between 0 and 12 h plasmolysis and remained stable after 24 h plasmolysis. During eight weeks induction of somatic embryogenesis, the callose content of explants plasmolyzed for 12 h was slightly higher than explants plasmolyzed for 6 or 24 h, with the largest differences observed after 6 weeks culture, which coincided with the maximum callose content and highest number of globular somatic embryos. The highest frequency of somatic embryo formation was observed in explants plasmolyzed for 12 h. The somatic embryo induction rate and number of somatic embryos per explant were markedly different in zygotic embryos pretreated with plasmolysis alone (78.0%, 43 embryos per explant) and those pretreated with plasmolysis and the callose synthase inhibitor 2-deoxy-d-glucose (11.5%, 8 embryos per explant). This study indicates that callose production is required for somatic embryogenesis in plasmolyzed explants.

Piptoporus betulinus, a brown-rot parasitic fungus of birch trees (Betula species), has been used as a common anti-parasitic and antibacterial agent. The lack of genetic resource data for P. betulinus has limited the exploration of this species. In this present study, we used Illumina Hiseq 2500 technology to examine the transcriptome assembly of P. betulinus in response to birch sawdust induction. By de novo assembly, 21,882 non-redundant unigenes were yielded, and 21,255 (97.1%) were annotated with known gene sequences. A total of 340 responsive unigenes were highly homologous with putative lignocellulose-degrading enzyme candidates. Additionally, 86 unigenes might be involved in the chemical reaction in xenobiotics biodegradation and metabolism, which suggests that this fungus could convert xenobiotic materials and has the potential ability to clean up environmental pollutants. To our knowledge, this was the first study on transcriptome sequencing and comparative analysis of P. betulinus, which provided a better understanding of molecular mechanisms underlying birch sawdust induction and identified lignocelluloses degrading enzymes.