This experiment was conducted to investigate the effects of heat stress (HS) on the feed intake, milk production and composition and metabolic alterations in the mammary gland of dairy cows.  Twenty Holstein cows were randomly assigned to one of two treatments according to a completely randomized design.  Half of the cows were allocated to the HS group in August (summer season), and the other half were assigned to the HS-free group in November (autumn season).  HS reduced (P<0.01) dry matter intake (DMI), milk yield, milk protein and milk urea nitrogen (MUN) of cows compared with HS-free control, but increased (P<0.01) milk somatic cell counts (SCC).  We determined the HS-induced metabolic alterations and the relevant mechanisms in dairy cows using liquid chromatography mass spectrometry combined with multivariate analyses.  Thirty-four metabolites were identified as potential biomarkers for the diagnosis of HS in dairy cows.  Ten of these metabolites, glucose, lactate, pyruvate, lactose, β-hydroxybutyrate, citric acid, α-ketoglutarate, urea, creatine, and orotic acid, had high sensitivity and specificity for HS diagnoses, and seven metabolites were also identified as potential biomarkers of HS in plasma, milk, and liver.  These substances are involved in glycolysis, lactose, ketone, tricarboxylic acid (TCA), amino acid and nucleotide metabolism, indicating that HS mainly affects lactose, energy and nucleotide metabolism in the mammary gland of lactating dairy cows.  This study suggested that HS might affect milk production and composition by affecting the feed intake and substance metabolisms in the mammary gland tissue of lactating dairy cows.

Plant N starvation response is closely associated with the N signaling components that involve transduction of the low-N cues.  In this study, we functionally characterized TaARR1, a cytokinin (CK) response regulator gene in Triticum aestivum, in mediating the N starvation adaptation in plants.  TaARR1 harbors two conserved domains specified by plant ARR family members; subcellular localization analysis indicated its target onto nucleus after endoplasmic reticulum assortment.  TaARR1 displayed modified expression upon the N starvation stressor, showing upregulated expression in roots and leaves over a 27-h N starvation treatment and whose induced transcripts were gradually recovered along with progression of the N recovery treatment.  The tobacco lines overexpressing TaARR1 displayed improved low-N stress tolerance, displaying enlarged phenotype, increased biomass and N accumulation, and enhanced glutamine synthetase (GS) activities compared with wild type (WT) following the N starvation treatment.  Expression analysis on genes encoding the nitrate transporter (NRT) and GS proteins in Nicotiana tabacum revealed that NtNRT2.2 and NtGS3 are upregulated in expression in the N-deprived transgenic lines, whose expression patterns were contrasted to other above family genes that were unaltered on transcripts between the transgenic lines and WT.  Transgene analysis validated the function of NtNRT2.2 and NtGS3 in regulating N accumulation, GS activity, growth traits, and N use efficiency in plants.  These results suggested the internal connection between the TaARR1-mediated N starvation tolerance and the modified transcription of distinct N acquisition- and assimilation-associated genes.  Our investigation together indicates that TaARR1 is essential in plant N starvation adaptation due to the gene function in transcriptionally regulating distinct NRT and GS genes that affect plant N uptake and assimilation under the N starvation condition.