Fish use their mucosal barriers to interact with their surroundings while maintaining homeostasis. Gill-associated lymphoid tissue (GIALT) provides an important initial line of defense against waterborne infections. We examined the morphology and ultrastructural characteristics of immune cells in the branchial epithelium of silver carp (Hypophthalmichthys molitrix) using histology and transmission electron microscopy. We processed samples from silver carp (n = 10) for semi-thin sectioning and transmission electron microscopy. We stained semi-thin sections with toluidine blue and methylene blue and ultrathin sections with uranyl acetate and lead citrate. We identified several immune cell types in the gill mucosa, including polymorphonuclear leukocytes with multilobed nuclei and three granule types: eosinophilic granular cells with crystalloid cores in their specific granules, and rodlet cells at granular and mature developmental stages. We identified mononuclear phagocytes (macrophages) in the lamina propria and gill lumen. In the basal and intermediate layers of the branchial epithelium, we observed cells with abundant rough endoplasmic reticulum and endo-lysosomal systems. We also observed apoptotic characteristics in the surface layer, including chromatin condensation and the expansion of rough endoplasmic reticulum. Our findings illustrate the complex cellular architecture of the branchial mucosal immune barrier in silver carp and establish a morphological basis for understanding the cellular components that influence gill-associated immunity.
Genome annotations frequently group DEETIOLATED2 (DET2), ECERIFERUM10 (CER10), and related proteins under broad steroid-reductase-like designations, despite experimentally characterized members participating in distinct metabolic pathways associated with plant development and environmental responses. Here, we comparatively characterized DET2 and CER10 related reductases in Arabidopsis thaliana, Amaranthus hypochondriacus, and the allotetraploid crop Chenopodium quinoa. Phylogenetic analysis resolved five groups and clearly separated DET2-like and CER10-like proteins. Conserved motifs, exon–intron organization, local microsynteny, and predicted membrane topology and protein structure further supported this distinction and the retention of paired quinoa loci following allopolyploidization. Public expression datasets revealed marked transcriptional differences among family members. Germination and expression analyses were subsequently performed in the quinoa accessions Giza1 and Puno (Q04), which showed contrasting responses to 250 mM NaCl. Q04 maintained rapid germination under salinity, whereas Giza1 displayed a pronounced delay and reduced final germination. Among four genes analysed by RT-qPCR, CqCER10.1 showed the clearest accession- and time-dependent expression pattern. Under 250 mM NaCl, CqCER10.1 transcript levels were significantly higher in Q04 than in Giza1 during early germination, coinciding with the markedly faster and more successful germination of Q04 under salinity. In Giza1, CqCER10.1 accumulation occurred later, broadly following its delayed germination progression. CqCER10.2 and CqDET2.2 remained weakly expressed, whereas CqDET2.1 accumulated mainly at later stages. Given the contrasting behaviour of the CER10-like copies (homoeologs), comparative analysis of their upstream regions in the QQ74 reference genome revealed substantial sequence divergence together with locally conserved regions and putative cis-regulatory elements. Overall, these results refine the classification of DET2- and CER10 related reductases in quinoa and reveal pronounced transcriptional asymmetry among retained gene copies. CqCER10.1 expression was associated with the contrasting germination behaviour of Giza1 and Q04, particularly under salinity. Whether this association reflects developmental progression, accession-specific regulation under salinity, or both remains to be determined.
Colleters are secretory emergences located near developing vegetative and reproductive meristems, traditionally associated with protecting young tissues against dehydration and microbial infection. The occurrence of colleters in eudicots is likely underestimated due to the scarcity of targeted anatomical studies. Here, we investigated the occurrence, distribution, structure, and histochemical composition of colleters in four Neotropical species of Lecythidaceae. Using light microscopy and scanning electron microscopy, we documented the distribution and anatomy of colleters at different developmental stages in Gustavia augusta L., Couroupita guianensis Aubl., Cariniana legalis (Mart.) Kuntze, and Lecythis pisonis Cambess. Colleters are conical and elongated, composed of a central parenchyma axis covered by a secretory epidermis with a well-developed cuticle. They occur in distinct positions in vegetative and reproductive organs: at the lateral extremities of the base of leaf primordia, corresponding to a stipular position, in an intrapetiolar position in G. augusta, and along the margins of developing leaves; in reproductive structures, they occur at the base of bracts and bracteoles in developing flowers of C. guianensis, C. legalis, and L. pisonis, and on the margins of the petals of C. guianensis. Histochemical analyses revealed a heterogeneous exudate composed mainly of mucilage associated with lipophilic, phenolic, proteinaceous, and terpenoid compounds. The occurrence of colleters near developing organs and the composition of their exudate are consistent with a potential protective function during organ development. These findings expand current knowledge about secretory structures in Lecythidaceae and provide a basis for further comparative studies of colleter diversity and secretion mechanisms in the family.
Filamentous fungi and oomycetes have four large intracellular membrane systems consisting of tubes, lamellae, or a combination thereof. Such elongated membrane structures can extend for tens of micrometers in hyphal cells, branching and connecting into bundles and networks. These systems are represented by tubular vacuoles, elongated mitochondria, endoplasmic reticulum, and macroinvaginations of the plasma membrane. They are most developed in xylotrophic and mycorrhiza-forming basidiomycetes. This review examines three membrane systems, excluding the macroinvaginations. Various morphotypes of these membrane systems, characteristic of certain taxonomic and ecological-trophic groups of fungi and oomycetes, are considered. Hypotheses explaining the role of large-scale membrane systems in the life processes of filamentous organisms are presented. These hypotheses are still relatively speculative because they rely more on morphology and topology than on the poorly studied physiology of these systems. The synthesizing hypothesis posits that, at least in the apical region of hyphae, tubular vacuoles, elongated mitochondria, and the endoplasmic reticulum interact closely and may facilitate intrahyphal solute transport, independent of mass flow and turgor gradients. Further studies of large-scale membrane systems are important for developing the structural physiology of filamentous fungi and other organisms.
Cinnamate 4-hydroxylase (C4H) is a key cytochrome P450 enzyme in the phenylpropanoid pathway, providing essential precursors for lignin and flavonoid biosynthesis. While well characterized in seed plants, the functional and regulatory features of C4H in lycophytes remain less well understood. In this study, a C4H gene (SmC4H) from the lycophyte Selaginella moellendorffii was cloned and functionally characterized. Sequence and comparative analyses showed that SmC4H retains the characteristic CYP73 framework, including a non-canonical PSRF sequence, and falls within the supported land-plant C4H/CYP73 cluster in a maximum-likelihood phylogeny. SmC4H also displayed the complete 10-motif architecture observed in the sampled land-plant C4Hs and a 3-exon/2-intron organization shared by many of these genes. Heterologous expression in yeast confirmed its cinnamate 4-hydroxylase activity, and kinetic analysis showed that SmC4H exhibited its highest apparent catalytic efficiency toward trans-cinnamic acid. In addition, SmC4H was capable of accepting the bulky cinnamate analog 2-naphthoic acid as a substrate, indicating a degree of substrate permissiveness. Subcellular localization analysis demonstrated that SmC4H is localized to the endoplasmic reticulum. Expression profiling revealed that SmC4H transcripts were most abundant in stems, which also exhibited the highest mean relative lignin content among the tissues examined. In contrast, flavonoid content was highly enriched in leaves, suggesting distinct tissue-level accumulation patterns of phenylpropanoid metabolites. Finally, promoter activity assays demonstrated that the SmC4H promoter (pSmC4H) is capable of driving gene expression in both vascular (Nicotiana benthamiana) and non-vascular (Marchantia polymorpha) plants. These findings provide a comparative reference for plant C4H biochemistry and promoter activity.
