Two <i>Mychonastes</i> isolated from freshwater bodies are novel potential feedstocks for biodiesel production

<p>Microalgae have been considered as ideal feedstocks for biodiesel production but the potential application is still under investigations. Here, eight kinds of microalgae were identified from water samples based on the morphologic and phylogenetic analyses. Among these eight microalgae, two <i>Mychonastes</i> S4 and S15 exhibited relative faster growth rate in the early culture stage and the highest contents of lipids. The two <i>Mychonastes</i> also showed higher C18:1 contents than the two <i>Chlorella</i> which were traditionally considered to be potential species for biodiesel production. As one kind of less researched microalgae, this study suggests <i>Mychonastes</i> should be a potential feedstock for biodiesel production. The application of the microalgal biodiesel still have some limiting factors, however, it is promising based on better lipid extraction technology and more relevant studies.</p

Genome-Wide Analysis of the NADK Gene Family in Plants

<div><p>Background</p><p>NAD(H) kinase (NADK) is the key enzyme that catalyzes <i>de novo</i> synthesis of NADP(H) from NAD(H) for NADP(H)-based metabolic pathways. In plants, NADKs form functional subfamilies. Studies of these families in <i>Arabidopsis thaliana</i> indicate that they have undergone considerable evolutionary selection; however, the detailed evolutionary history and functions of the various NADKs in plants are not clearly understood.</p><p>Principal Findings</p><p>We performed a comparative genomic analysis that identified 74 NADK gene homologs from 24 species representing the eight major plant lineages within the supergroup Plantae: glaucophytes, rhodophytes, chlorophytes, bryophytes, lycophytes, gymnosperms, monocots and eudicots. Phylogenetic and structural analysis classified these NADK genes into four well-conserved subfamilies with considerable variety in the domain organization and gene structure among subfamily members. In addition to the typical NAD_kinase domain, additional domains, such as adenylate kinase, dual-specificity phosphatase, and protein tyrosine phosphatase catalytic domains, were found in subfamily II. Interestingly, NADKs in subfamily III exhibited low sequence similarity (∼30%) in the kinase domain within the subfamily and with the other subfamilies. These observations suggest that gene fusion and exon shuffling may have occurred after gene duplication, leading to specific domain organization seen in subfamilies II and III, respectively. Further analysis of the exon/intron structures showed that single intron loss and gain had occurred, yielding the diversified gene structures, during the process of structural evolution of NADK family genes. Finally, both available global microarray data analysis and qRT-RCR experiments revealed that the NADK genes in <i>Arabidopsis</i> and <i>Oryza sativa</i> show different expression patterns in different developmental stages and under several different abiotic/biotic stresses and hormone treatments, underscoring the functional diversity and functional divergence of the NADK family in plants.</p><p>Conclusions</p><p>These findings will facilitate further studies of the NADK family and provide valuable information for functional validation of this family in plants.</p></div

Abiotic/biotic stress and hormone response elements in <i>AtNADK</i> and <i>OsNADK</i> promoters^*.

<p>*the <i>cis</i>-elements were identified with the PlantCARE program (<a href="http://bioinformatics.psb.ugent.be/webtools/plantcare/html/" target="_blank">http://bioinformatics.psb.ugent.be/webtools/plantcare/html/</a>) using the sequences 1500 bp upstream from the transcription start site of each NADK gene. The “√” means the NADK gene contains this <i>cis</i>-element in the promoter region.</p

Systematic evolutionary relationships of 24 species among eight lineages within the supergroup Plantae.

<p>The numbers of NADK homologs in each species are listed next to the tree. *, the genome sequencing of <i>Picea sitchensis</i> is not complete.</p

Expression patterns of NADK family genes in <i>Arabidopsis</i> under abiotic stress and hormone treatments.

<p>Expression levels of <i>AtNADK1–3</i> assayed by qRT-PCR under cold (4°C), heat (30°C), drought (20% PEG6000), salt (200 mM NaCl), oxidative (30 µM MV) stresses and MeJA (100 µM), ABA (100 µM) hormone treatments. Data are means ± SD (n = 3) and are representative of similar results from three independent experiments.</p

The expansion and evolution of the NADK gene family in plants.

<p>(<b>A</b>) Schematic comparison of intron distribution in NADK orthologs of land plants generated with the CIWOG software. Black horizontal lines are aligned sequences; gray horizontal lines are gaps in the alignment; gray vertical bars are conserved common introns; red vertical bars are gained introns. The numbers 0, 1 and 2 are intron phases. (<b>B</b>) A model for the expansion and evolution of the NADK gene family in Plantae.</p

Expression patterns of NADK family genes in rice under abiotic stress and hormone treatments.

<p>Expression levels of <i>OsNADK1–4</i> assayed by qRT-PCR under cold (4°C), heat (30°C), drought (20% PEG6000), salt (200 mM NaCl), oxidative (30 µM MV) stresses and MeJA (100 µM), ABA (100 µM) hormone treatments. Data are means ± SD (n = 3) and are representative of similar results from three independent experiments.</p

Phylogenetic relationships and domain organization of NADK genes in plants.

<p>(<b>A</b>) The rooted maximum-likelihood phylogenetic tree of NADK family members was inferred from the amino acid sequence alignment of the NAD_kinase domain. Numbers above the nodes represent bootstrap values from 1000 replications. (<b>B</b>) Domain organization of the NADKs. (<b>C</b>) Amino acid sequence alignment of conserved motifs within the NAD_kinase domain.</p

Image_3_BIN2 phosphorylates the Thr280 of CO to restrict its function in promoting Arabidopsis flowering.tif

CONSTANS (CO) is a central regulator of floral initiation in response to photoperiod. In this study, we show that the GSK3 kinase BIN2 physically interacts with CO and the gain-of-function mutant bin2-1 displays late flowering phenotype through down-regulation of FT transcription. Genetic analyses show that BIN2 genetically acts upstream of CO in regulating flowering time. Further, we illustrate that BIN2 phosphorylates the Thr280 residue of CO. Importantly, the BIN2 phosphorylation of Thr280 residue restricts the function of CO in promoting flowering through affecting its DNA-binding activity. Moreover, we reveal that the N-terminal part of CO harboring the B-Box domain mediates the interaction of both CO-CO and BIN2-CO. We find that BIN2 inhibits the formation of CO dimer/oligomer. Taken together, this study reveals that BIN2 regulates flowering time through phosphorylating the Thr280 of CO and inhibiting the CO-CO interaction in Arabidopsis.</p

Image_2_BIN2 phosphorylates the Thr280 of CO to restrict its function in promoting Arabidopsis flowering.tif

CONSTANS (CO) is a central regulator of floral initiation in response to photoperiod. In this study, we show that the GSK3 kinase BIN2 physically interacts with CO and the gain-of-function mutant bin2-1 displays late flowering phenotype through down-regulation of FT transcription. Genetic analyses show that BIN2 genetically acts upstream of CO in regulating flowering time. Further, we illustrate that BIN2 phosphorylates the Thr280 residue of CO. Importantly, the BIN2 phosphorylation of Thr280 residue restricts the function of CO in promoting flowering through affecting its DNA-binding activity. Moreover, we reveal that the N-terminal part of CO harboring the B-Box domain mediates the interaction of both CO-CO and BIN2-CO. We find that BIN2 inhibits the formation of CO dimer/oligomer. Taken together, this study reveals that BIN2 regulates flowering time through phosphorylating the Thr280 of CO and inhibiting the CO-CO interaction in Arabidopsis.</p