Insects are the only known animals in which sexual differentiation is controlled by sex-specific splicing. The doublesex transcription factor produces distinct male and female isoforms, which are both essential for sex-specific development. dsx splicing depends on transformer, which is also alternatively spliced such that functional Tra is only present in females. This pathway has evolved from an ancestral mechanism where dsx was independent of tra and expressed and required only in males. To reconstruct this transition, we examined three basal, hemimetabolous insect orders: Hemiptera, Phthiraptera, and Blattodea. We show that tra and dsx have distinct functions in these insects, reflecting different stages in the changeover from a transcription-based to a splicing-based mode of sexual differentiation. We propose that the canonical insect tra-dsx pathway evolved via merger between expanding dsx function (from males to both sexes) and narrowing tra function (from a general splicing factor to dedicated regulator of dsx).
The recruitment of a bacterial consortium by the host is a strategy not limited to animals but is also used in plants.A maize aerial root mucilage has been found that harbors nitrogen fixing bacteria that are attracted to the carbohydrate rich environment. This synbiotic relationship is facilitated by a polysaccharide, whose complicated structure has been previously unknown. In this report, we present the characterization of the maize polysaccharide by employing new analytical strategies combining chemical depolymerization, oligosaccharide sequencing, and monosaccharide and glycosidic linkage quantitation. The mucilage contains a single heterogeneous polysaccharide composed of a highly fucosylated and xylosylated galactose backbone with arabinan and mannoglucuronan branches. This unique polysaccharide structure may select for the diazotrophic community by containing monosaccharides and linkages that correspond to the glycosyl hydrolases associated with the microbial community. The elucidation of this complicated structure illustrates the power of the analytical methods, which may serve as a general platform for polysaccharide analysis in the future.
A rapid method for the quantitation of sixteen neutral and acidic monosaccharides, from both animal and plant sources was developed using ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UHPLC/QqQ-MS) in dynamic multiple reaction monitoring (dMRM) mode. Monosaccharides including three pentoses (ribose, xylose, arabinose), two deoxyhexoses (rhamnose, fucose), five hexoses (fructose, mannose, allose, glucose, galactose), two hexuronic acids (glucuronic acid, galacturonic acid), and two N-acetyl-hexosamines (GlcNAc, GalNAc), were derivatized with 1-phenyl-3-methyl-5-pyrazolone (PMP), while underivatized sialic acids, N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc), were simultaneously analyzed with a 10-minute run. With the optimized UHPLC conditions, baseline separations of the isomers were achieved. The sensitivity and calibration ranges of this method were determined. The limits of detection were between femtomoles and attomoles with linear ranges spanning four to six orders of magnitude and CVs ≤ 7.2%. Spiking experiments performed on a pooled fecal sample demonstrated the high accuracy of this method even when applied to samples with complicated matrices. The validated method was applied to fecal samples from an infant transitioning from breast milk to weaning foods. Major milk monosaccharides including galactose, fucose, glucose, GlcNAc, and Neu5Ac were found to be the most abundant components in the feces of milk-fed infants. PMP-derivatives of other monosaccharides including apiose, lyxose, altrose, talose, gulose, glucosamine, galactosamine, mannosamine, and N-acetylmannosamine (ManNAc) were also tested and could be added to the quantitation method depending on the need. The speed and sensitivity of the method makes it readily adaptable to rapid throughput analysis of monosaccharides in biological samples.
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