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Hypoglycemia triggers autonomic and endocrine counter-regulatory responses to restore glucose homeostasis, a response that is impaired in patients with diabetes and its long-term complication hypoglycemia-associated autonomic failure (HAAF). We show that insulin-evoked hypoglycemia is severely aggravated in mice lacking the cation channel proteins TRPC1, TRPC4, TRPC5, and TRPC6, which cannot be explained by alterations in glucagon or glucocorticoid action. By using various TRPC compound knockout mouse lines, we pinpointed the failure in sympathetic counter-regulation to the lack of the TRPC5 channel subtype in adrenal chromaffin cells, which prevents proper adrenaline rise in blood plasma. Using electrophysiological analyses, we delineate a previously unknown signaling pathway in which stimulation of PAC1 or muscarinic receptors activates TRPC5 channels in a phospholipase-C-dependent manner to induce sustained adrenaline secretion as a crucial step in the sympathetic counter response to insulin-induced hypoglycemia. By comparing metabolites in the plasma, we identified reduced taurine levels after hypoglycemia induction as a commonality in TRPC5-deficient mice and HAAF patients., (© 2024. The Author(s).)

Background: The citrus genus comprises a number of sensitive tropical and subtropical species to cold stress, which limits global citrus distribution to certain latitudes and causes major economic loss. We used RNA-Seq technology to analyze changes in the transcriptome of Valencia delta seedless orange in response to long-term cold stress grafted on two frequently used citrus rootstocks: Carrizo citrange (CAR), considered one of the most cold-tolerant accessions; C. macrophylla (MAC), a very sensitive one. Our objectives were to identify the genetic mechanism that produce the tolerant or sensitive phenotypes in citrus, as well as to gain insights of the rootstock-scion interactions that induce the cold tolerance or sensitivity in the scion., Results: Plants were kept at 1 ºC for 30 days. Samples were taken at 0, 15 and 30 days. The metabolomic analysis showed a significant increase in the concentration of free sugars and proline, which was higher for the CAR plants. Hormone quantification in roots showed a substantially increased ABA concentration during cold exposure in the CAR roots, which was not observed in MAC. Different approaches were followed to analyze gene expression. During the stress treatment, the 0-15-day comparison yielded the most DEGs. The functional characterization of DEGs showed enrichment in GO terms and KEGG pathways related to abiotic stress responses previously described in plant cold adaption. The DEGs analysis revealed that several key genes promoting cold adaption were up-regulated in the CAR plants, and those repressing it had higher expression levels in the MAC samples., Conclusions: The metabolomic and transcriptomic study herein performed indicates that the mechanisms activated in plants shortly after cold exposure remain active in the long term. Both the hormone quantification and differential expression analysis suggest that ABA signaling might play a relevant role in promoting the cold hardiness or sensitiveness of Valencia sweet orange grafted onto Carrizo citrange or Macrophylla rootstocks, respectively. Our work provides new insights into the mechanisms by which rootstocks modulate resistance to abiotic stress in the production variety grafted onto them., (© 2022. The Author(s).)

Background: Interspecific hybridizations and admixtures were key in Citrus domestication, but very little is known about their impact at the transcriptomic level. To determine the effects of genome introgressions on gene expression, the transcriptomes of the pulp and flavedo of three pure species (citron, pure mandarin and pummelo) and four derived domesticated genetic admixtures (sour orange, sweet orange, lemon and domesticated mandarin) have been analyzed at color break., Results: Many genes involved in relevant physiological processes for domestication, such sugar/acid metabolism and carotenoid/flavonoid synthesis, were differentially expressed among samples. In the low-sugar, highly acidic species lemon and citron, many genes involved in sugar metabolism, the TCA cycle and GABA shunt displayed a reduced expression, while the P-type ATPase CitPH5 and most subunits of the vacuolar ATPase were overexpressed. The red-colored species and admixtures were generally characterized by the overexpression in the flavedo of specific pivotal genes involved in the carotenoid biosynthesis, including phytoene synthase, ζ-carotene desaturase, β-lycopene cyclase and CCD4b, a carotenoid cleavage dioxygenase. The expression patterns of many genes involved in flavonoid modifications, especially the flavonoid and phenylpropanoid O-methyltransferases showed extreme diversity. However, the most noticeable differential expression was shown by a chalcone synthase gene, which catalyzes a key step in the biosynthesis of flavonoids. This chalcone synthase was exclusively expressed in mandarins and their admixed species, which only expressed the mandarin allele. In addition, comparisons between wild and domesticated mandarins revealed that the major differences between their transcriptomes concentrate in the admixed regions., Conclusion: In this work we present a first study providing broad evidence that the genome introgressions that took place during citrus domestication largely shaped gene expression in their fruits., (© 2022. The Author(s).)

We performed genomic analyses on wild species of the genus Citrus to identify major determinants of evolution. The most notable effect occurred on the pathogen-defense genes, as observed in many other plant genera. The gene space was also characterized by changes in gene families intimately related to relevant biochemical properties of citrus fruit, such as pectin modifying enzymes, HDR (4-hydroxy-3-methylbut-2-enyl diphosphate reductase) genes, and O-methyltransferases. Citrus fruits are highly abundant on pectins and secondary metabolites such as terpenoids and flavonoids, the targets of these families. Other gene types under positive selection, expanded through tandem duplications and retained as triplets from whole genome duplications, codified for purple acid phosphatases and MATE-efflux proteins. Although speciation has not been especially rapid in the genus, analyses of selective pressure at the codon level revealed that the extant species evolved from the ancestral citrus radiation show signatures of pervasive adaptive evolution and is therefore potentially responsible for the vast phenotypic differences observed among current species., (© 2021 The Authors. The Plant Genome published by Wiley Periodicals LLC on behalf of Crop Science Society of America.)

We performed genomic analyses on species and varieties of the genus Citrus to identify several determinants of domestication, based on the pattern of pummelo [Citrus maxima (Burr. f) Merr] and mandarin (Citrus reticulata Blanco) admixture into the ancestral genome, as well as population genetic tests at smaller scales. Domestication impacted gene families regulating pivotal components of citrus flavor (such as acidity) because in edible mandarin varieties, chromosome areas with negative Tajimas values were enriched with genes associated with the regulation of citric acid. Detection of sweeps in edible mandarins that diverged from wild relatives indicated that domestication reduced chemical defenses involving cyanogenesis and alkaloid synthesis, thus increasing palatability. Also, a cluster of SAUR genes in domesticated mandarins derived from the pummelo genome appears to contain candidate genes controlling fruit size. Similarly, conserved stretches of pure mandarin areas were likely important as well for domestication, as, for example, a fragment in chromosome 1 that is involved in the apomictic reproduction of most edible mandarins. Interestingly, our results also support the hypothesis that various genes subject to selective pressure during evolution or derived from whole genome duplication events later became potential targets of domestication., (© 2021 The Authors. The Plant Genome published by Wiley Periodicals LLC on behalf of Crop Science Society of America.)