The photosynthetic performance and photoprotective role of carotenoids response to light stress in intertidal red algae Neoporphyra haitanensis.

Neoporphyra haitanensis, a red alga harvested for food, thrives in the intertidal zone amid dynamic and harsh environments. High irradiance represents a major stressor in this habitat, posing a threat to the alga's photosynthetic apparatus. Interestingly, N. haitanensis has adapted to excessive light despite the absence of a crucial xanthophyll cycle-dependent photoprotection pathway. Thus, it is valuable to investigate the mechanisms by which N. haitanensis copes with excessive light and to understand the photoprotective roles of carotenoids. Under high light intensities and prolonged irradiation time, N. haitanensis displayed reduction in photosynthetic efficiency and phycobiliproteins levels, as well as different responses in carotenoids. The decreased carotene contents suggested their involvement in the synthesis of xanthophylls, as evidenced by the up-regulation of lycopene-ß-cyclase (lcyb) and zeaxanthin epoxidase (zep) genes. Downstream xanthophylls such as lutein, zeaxanthin, and antheraxanthin increased proportionally to light stress, potentially participating in scavenging reactive oxygen species (ROS). When accompanied by the enhanced activity of ascorbate peroxidase (APX), these factors resulted in a reduction in ROS production. The responses of intermediates α-cryptoxanthin and ß-cryptoxanthin were felt somewhere between carotenes and zeaxanthin/lutein. Furthermore, these changes were ameliorated when the organism was placed in darkness. In summary, down-regulation of the organism's photosynthetic capacity, coupled with heightened xanthophylls and APX activity, activates photoinhibition quenching (qI) and antioxidant activity, helping N. haitanensis to protect the organism from the damaging effects of excessive light exposure. These findings provide insights into how red algae adapt to intertidal lifestyles.

Glycolytic enzyme PKM2 regulates cell senescence but not inflammation in the process of osteoarthritis.

Chondrocyte senescence is an important mechanism underlying osteoarthritis in the senile population and is characterized by reduced expressions of the extracellular matrix proteins. The involvement of glycolysis and the tricarboxylic acid cycle in the development of osteoarthritis is inclusive. The present study aims to investigate the role of the glycolytic enzyme M2 isoform of pyruvate kinase (PKM2) in chondrocytes in senescence and inflammation. Primary chondrocytes are isolated from the knee joints of neonatal mice. Small interfering RNAs (siRNAs) against PKM2 are transfected using lipofectamine. RNA sequencing is conducted in primary chondrocytes with the PKM2 gene deleted. Cell apoptosis, autophagy, reactive oxygen species measurement, and senescent conditions are examined. The glycolytic rate in cells is measured by Seahorse examination. Interleukin 1-ß (IL-1ß) increases the protein expressions of matrix metallopeptidases (MMP)13 and PKM2 and reduces the protein expression of collagen type II (COL2A1) in primary chondrocytes. Silencing of PKM2 alters the protein expressions of MMP13, PKM2, and COL2A1 in the same pattern in quiescent and stimulated chondrocytes. RNA sequencing analysis reveals that PKM2 silencing reduces senescent biomarker p16 INK4a expression. Compared with low-passage chondrocytes, high-passage chondrocytes exhibit increased expression of p16 INK4a and reduced expression of COL2A1. Silencing of PKM2 reduces SA-ß-Gal signals and increases COL2A1 expression in high-passage chondrocytes. Seahorse assay reveals that PKM2 deletion favors the tricarboxylic acid cycle in mitochondria in low- but not in high-passage chondrocytes. In summary, the glycolytic enzyme PMK2 modulates chondrocyte senescence but does not participate in the regulation of inflammation.

Insights into the Ancient Adaptation to Intertidal Environments by Red Algae Based on a Genomic and Multiomics Investigation of Neoporphyra haitanensis.

Colonization of land from marine environments was a major transition for biological life on Earth, and intertidal adaptation was a key evolutionary event in the transition from marine- to land-based lifestyles. Multicellular intertidal red algae exhibit the earliest, systematic, and successful adaptation to intertidal environments, with Porphyra sensu lato (Bangiales, Rhodophyta) being a typical example. Here, a chromosome-level 49.67 Mb genome for Neoporphyra haitanensis comprising 9,496 gene loci is described based on metagenome-Hi-C-assisted whole-genome assembly, which allowed the isolation of epiphytic bacterial genome sequences from a seaweed genome for the first time. The compact, function-rich N. haitanensis genome revealed that ancestral lineages of red algae share common horizontal gene transfer events and close relationships with epiphytic bacterial populations. Specifically, the ancestor of N. haitanensis obtained unique lipoxygenase family genes from bacteria for complex chemical defense, carbonic anhydrases for survival in shell-borne conchocelis lifestyle stages, and numerous genes involved in stress tolerance. Combined proteomic, transcriptomic, and metabolomic analyses revealed complex regulation of rapid responses to intertidal dehydration/rehydration cycling within N. haitanensis. These adaptations include rapid regulation of its photosynthetic system, a readily available capacity to utilize ribosomal stores, increased methylation activity to rapidly synthesize proteins, and a strong anti-oxidation system to dissipate excess redox energy upon exposure to air. These novel insights into the unique adaptations of red algae to intertidal lifestyles inform our understanding of adaptations to intertidal ecosystems and the unique evolutionary steps required for intertidal colonization by biological life.

Leakage coupling of ultrasensitive periodical silica thin-film long-period grating coated on tapered fiber.

This investigation demonstrates leakage coupling between fundamental-mode and high-order mode resonance based on a periodical silica thin-film long-period grating (TFLPG) that was coated on a tapered fiber when wavelengths longer than the fundamental-mode cutoff were propagated. For the leaky guiding situation, these leakage modes still may exhibit strong mode coupling in the taper with the assistance of the TFLPG when the phase-matched condition is satisfied. An extremely high tuning efficiency of 62.9 nm/°C, which is equivalent to a measurement of sensitivity of approximately 168, 182 nm per refractive index unit, is achieved. To the best of our knowledge, this sensitivity is the highest achieved for a fiber sensor to date.