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Alexandrium pacificum is a toxin-producing dinoflagellate with allelopathic effects. The elucidation of allelopathic mechanism of A. pacificum is of great significance for understanding A. pacificum blooms. To this end, using the model diatom Thalassiosira pseudonana as a target species, we observed changes in physiological, biochemical and gene transcription of T. pseudonana upon being co-cultured with A. pacificum. We found reciprocal effects between A. pacificum and T. pseudonana, and corroborated A. pacificum's allelopathy on T. pseudonana by observing inhibitory effects of filtrate from A. pacificum culture on the growth of T. pseudonana. We also found that co-culturing with A. pacificum, the expression of T. pseudonana genes related to photosynthesis, oxidative phosphorylation, antioxidant system, nutrient absorption and energy metabolism were drastically influenced. Coupled with the alterations in Fv/Fm (the variable/maximum fluorescence ratio), activity of superoxide dismutase, contents of malondialdehyde, neutral lipid and total protein in T. pseudonana co-cultured with A. pacificum, we propose that A. pacificum allelopathy could reduce the efficiency of photosynthesis and energy metabolism of T. pseudonana and caused the oxidative stress, while the nutrient absorption was also affected by allelopathic effects. The resultant data potentially uncovered the allelopathic molecular mechanism of A. pacificum to model alga T. pseudonana. The changes in nutrient uptake and even energy metabolism in T. pseudonana, as an adaptation to environmental conditions, may prevent it from stress-related injuries. Our finding might advance the understanding of allelopathic mechanism of A. pacificum.

Chronic pancreatitis (CP) is a progressive fibroinflammatory syndrome of the pancreatic tissue caused by genetic and environmental factors. Previously reported susceptibility genes in CP explain less than half of the apparent heritability. To uncover novel pathogenic mechanisms, we initially performed low-coverage whole-genome sequencing on 464 Chinese CP patients and 504 controls. The transient receptor potential cation channel, Subfamily V, Member 6 (TRPV6) gene was found to be significantly associated with CP after a burden test of aggregated rare nonsynonymous variants with a combined annotation dependent depletion score > 20 (p = .020). In the replication stage, we analyzed the entire coding sequence and exon/intron boundaries of the TPRV6 gene by Sanger sequencing in another 205 patients with CP and 105 controls. Integration of the findings from the two stages resulted in the identification of 25 TRPV6 variants: 1 rare nonsense variant, 20 rare missense variants, and 4 common missense variants. Loss-of-function variants, as determined by intracellular Ca2+ concentration in transfected HEK293T cells, were significantly overrepresented in patients as compared to controls (9/669 [1.35%] vs. 1/609 [0.16%]; odds ratio = 8.29; p = .022). This study provides evidence suggesting that TRPV6 is a novel susceptibility gene for CP.

Prorocentrum lima is a typical diarrheic shellfish poisoning (DSP) toxin-producing benthic dinoflagellate usually found attached to or associated with macrophytes, floating detritus, debris, or other substrates. In this paper, to gain a deeper understanding of the molecular and cellular responses to N limitation in P. lima, transcriptome profiling was performed. We found that most genes related to photosynthesis, porphyrin and chlorophyll metabolism were down-regulated following N limitation, while some genes concerning fatty acid biosynthesis, starch synthesis and ubiquitin pathway were up-regulated. Meanwhile, ABC transports ABCB1 and ABCG2 and glutathione S-transferase were up-regulated under N-limited conditions. These transcriptomic data were further corroborated by the biochemical analyses which revealed that starch, lipid content was increased, while photosynthetic efficiency was decreased. In addition, TEM analysis demonstrated that chloroplasts appeared smaller and were less abundant, while a major fraction of the cell volume was occupied by lipid bodies and starch granules, and thylakoid was twisted in the cells. Taking together, we proposed that N limitation could induce the accumulation of neutral lipid and starch in P. lima cells for carbon fixation trough recycling chloroplast membranes by autophagy. ABCB and ABCG transporters might be involved in the transport of DSP toxins. Our findings might provide global information for the response or adaptation of P. lima to N limitation.

OBJECTIVE. Chronic pancreatitis is a progressive, relapsing inflammatory disorder of the pancreas, which often develops in the background of genetic susceptibility. Recently, loss-of-function mutations in CPA1, which encodes the digestive enzyme carboxypeptidase A1, were described in sporadic early-onset cases and in hereditary pancreatitis. Mutation-induced misfolding of CPA1 and associated endoplasmic reticulum (ER) stress was suggested as potential disease mechanism, however, in vivo evidence has been lacking. The objective of the present study was to create a mouse model that recapitulates features of CPA1−associated chronic pancreatitis. DESIGN. We knocked-in the most frequently occurring p.N256K human CPA1 mutation to the mouse Cpa1 locus. Mutant mice were characterized with respect to pancreas pathology and ER stress and compared to C57BL/6N and CPA1 null control mice. RESULTS. In the CPA1 N256K mutant mice we observed hallmarks of chronic pancreatitis that included progressive acinar cell atrophy, inflammatory cell infiltration, fibrosis and acinar-ductal metaplasia. In contrast, similarly to the C57BL/6N mice, the CPA1 null control strain exhibited no signs of pancreatic disease. Mutation p.N256K induced misfolding of mouse CPA1 and resulted in elevated expression of ER stress markers Hspa5 (BiP) and Ddit3 (CHOP) both in cell culture and mutant mice. CONCLUSION. The results offer categorical evidence that CPA1 mutations elicit enzyme misfolding and cause chronic pancreatitis via an ER-stress related mechanism.

Karenia mikimotoi is an important toxin-producing dinoflagellate, frequently forming blooms along the coast of China. It has been shown that K. mikimotoi has allelopathic effects on other organisms, which benefited it over other microalgal species in competition. However, the underlying allelopathy mechanisms remain largely unclear. Thalassiosira pseudonana, a worldwide-distributed planktonic diatom, is extensively used as a model in diatom physiology studies. Here, we investigated the responses of T. pseudonana to K. mikimotoi allelopathy when they were co-cultured under laboratory condition. We found that there were reciprocal inhibitory effects between K. mikimotoi and T. pseudonana, and the cell-free filtrate of K. mikimotoi also deeply suppressed the growth of T. pseudonana, corroborating that K. mikimotoi allelopathy mainly accounted for the inhibition of K. mikimotoi against T. pseudonana. After exposed to K. mikimotoi allelopathy, the photosynthetic efficiency, contents of neutral lipid and malondialdehyde (MDA), as well as superoxide dismutase (SOD) activity in T. pseudonana were significantly changed. Meanwhile, the expression of genes involved in photosynthesis, oxidative phosphorylation, detoxifying system and nutrients uptake including PsbO, chlorophyll synthase (ChlG), risp1, ferredoxin-NADP+ reductase (PetH), ABCB1, nitrate transporters 1 (NRT1), phosphate transporter (PHT), alkaline phosphatase (ALP) and ascorbate peroxidase (APX) in T. pseudonana dramatically altered. These results suggested that K. mikimotoi could highly affect the efficiency of photosynthesis and energy metabolism of T. pseudonana, and also inhibit the nutrients uptake and assimilation. Our findings might provide insight information for the K. mikimotoi allelopathy.