Chinese tallow ( Triadica sebifera ) is an oil-seed producing tree with a great potential as a biofuel crop and does not compete with food crops for land. The fruits are unique in that they contain two kinds of lipid, a highly un-saturated oil and a saturated fat separated in the seed and an external tallow layer respectively. However, until recently it was unclear whether the tallow is a non-seed tissue or an external fat deposition. We have addressed this important question by scanning electron microscopy to show that it is a cellular tissue and provided biochemical evidence for an active storage oil or triacylglycerol (TAG) biosynthetic machinery in the non-seed tallow tissue. We also showed that tallow tissue accumulates more TAG and has a different fatty acid profile compared to the seed TAG. As a sequence resource to aid the development of this oil crop, we generated a transcriptome resource by sequencing three component fruit tissues of tallow, seed and fruit coat. This enabled the reconstruction of lipid biosynthesis pathway in this potential biofuel crop. The transcriptome resource has thus far allowed identification of key differences in oil synthesis and storage mechanisms between the seed and tallow tissues. This non-seed oil accumulating tissue can be used as model system to gain further knowledge of such tissues to facilitate efficient utilization of non-seed biomass for oil production.
The movement of water is a matter of great importance to all plant species. This is particularly true for the rubber tree ( Hevea brasiliensis Muell. Arg.) which is tapped for the laticifer cytoplasm in the form of aqueous latex. Due to the lack of plasmodesmata, the laticifer water balance is mediated largely by aquaporins (AQPs), a class of channel-forming integral membrane proteins that transport water and other small solutes. Our studies reported the characterization of 51 full-length AQP genes from the rubber tree genome, and further assigned them to five subfamilies, i.e. plasma membrane intrinsic proteins (PIPs: 15), tonoplast intrinsic proteins (TIPs: 17), NOD26-like intrinsic proteins (NIPs: 9), small basic intrinsic proteins (SIPs: 4) and X intrinsic proteins (XIPs: 6). Although the classification of subfamily/subgroup is the same as in Ricinus communis , genome-wide comparative analysis revealed the PIP and TIP subfamilies in rubber tree are highly expanded, corresponding to their high water permeability and the particular importance of water balance in a big tree and a highly differentiated laticifer tissue. Functional prediction based on the analysis of the aromatic/arginine (ar/R) selectivity filter, Froger’s positions and specificity-determining positions (SDPs) further suggested the potentially key role of HbPIPs and HbTIPs in the laticifer water balance. Moreover, deep sequencing of the latex transcriptome and qRT-PCR analysis supported a crucial role of several PIP subfamily members in the laticifer water balance under both normal and ethephon-stimulated conditions.
Hemoglobin plays an important role in oxygen transfer from respiratory surfaces to metabolizing tissues. Evidence from other vertebrate taxa suggests that the specific amino acid changes in key positions of hemoglobin or structural changes in the hemoglobin proteins play important roles in controlling Hb-O 2 affinity, as well as helping high-attitude animals to adapt to high altitude hypoxia. Pikas and zokor are keystone species in the Tibetan plateau ecosystem and are considered to be genetically adapted to extremely hypoxic environment. In the present study, the α and β globin gene sequences from four species of pikas and one species of zokor were obtained and then conducted molecular evolutionary analysis. Our study provides evidence of positive selection on pikas and zokor α and β globins and demonstrates adaptive evolution of pikas and zokor α and β globins that could affect the ability of hemoglobin to bind to oxygen. These findings increase the knowledge contributes to the understanding of adaptive evolutionary of pikas and zokor to high altitude hypoxic conditions of the Qinghai-Tibetan Plateau. Nevertheless, further functional experiments will be required to test the findings in this study.
The causal link between a pathogen’s gene and virulence can be established by fulfilling Molecular Koch’s Postulates, which, in turn, requires the engineering of targeted mutations in the predicted gene of interest. Within the past decade, the paradigm-shifting and revolutionary technology of recombineering has enabled bacteriologists to construct virtually every conceivable mutation in many enteric bacteria. Recombineering exploits the function of bacteriophage-encoded recombinases to bring about allelic replacement. In recombineering, a linear double stranded or single stranded DNA molecule with terminal homology arms, identical to the region upstream and downstream of a genetic locus of interest, is introduced into hyperrecombinogenic bacteria. Recombinases catalyze the replacement of the endogenous allele with the introduced allele by means of a double crossover event. Using this technique, researchers have methodically dissected the virulence repertoire of the attaching and effacing (A/E) pathogens including enteropathogenic Escherichia coli (EPEC), enterohermorrhagic E. coli (EHEC), and Citrobacter rodentium . In contrast, the virulome of the most recent family member, E. albertii , remains unmapped, despite metagenomic sequencing revealing that the bacterium possesses an impressive arsenal of virulence determinants. Moreover, numerous retrospective studies have incriminated E. albertii as the etiologic agent of multiple disease outbreaks in both developed and developing countries. Yet, its pathogenic potential remains cryptic. Therefore, it is imperative to initiate studies to interrogate its virulence mechanisms for developing effective interventions. With this in mind, we developed a lambda red-mediated recombineering protocol to identify and characterize virulence genes in the bacterium. The versatility of recombineering for targeted mutagenesis was demonstrated by allelic replacement of multiple unlinked genetic loci, with a noted role in the virulence of related A/E pathogens. Our protocol will enable researchers to mutagenize any gene in E. albertii to have a concrete understanding of its contribution to bacterial physiology and virulence.
A PARP1-Erk2 synergism was required to generate synaptic long-term potentiation in the CA3-CA1 hippocampal connections. This molecular mechanism was associated with the recently identified pivotal role of polyADP-ribosylation in learning. High frequency electrical stimulation of cortical and hippocampal neurons induced binding of phosphorylated Erk2 (transported into the nucleus) to the nuclear protein PARP1. PARP1-Erk2 binding induced PARP1 activation and polyADP-ribosylation of its prominent substrate, linker histone H1. A facilitated access of PARP1-bound phosphorylated Erk2 to its substrates, transcription factors Elk1 and CREB was attributed to the release of polyADP-ribosylated H1 from the DNA, causing local DNA relaxation. Erk-induced phosphorylation of transcription factors activating the HAT activity of CBP (CREB binding protein), recruited acetylated histone H4 to the promoters of immediate early genes (IEG) cfos, zif268 and arc, which are implicated in synaptic plasticity. In accordance, their induced expression was suppressed after PARP1 genetic deletion in PARP1-KO mice, or after PARP1 inhibition or silencing. Moreover, under these conditions, long-term synaptic potentiation (LTP) (indicating synaptic plasticity) was not generation in the hippocampal CA3-CA1 connections, and learning abilities were impaired. Furthermore, both IEG expression and LTP generation failed when cerebral neurons accumulated single strand DNA breaks, due to a predominant binding of PARP1 to nicked DNA, occluding its Erk binding sites. Thus, a declined synaptic plasticity is anticipated when aged cerebral neurons accumulate DNA single-strand breaks during life span.
