Investigating the Mechanisms Underlying the Low Irradiance-Tolerance of the Economically Important Seaweed Species Pyropia haitanensis.

Pyropia haitanensis, one of the most economically and ecologically important seaweed species, is often exposed to persistent or transient low irradiance (LI), resulting in limited yield and quality. However, the mechanisms mediating P. haitanensis responses to LI are largely unknown. In this study, LI-tolerant (LIT) and LI-sensitive (LIS) P. haitanensis strains were compared regarding their physiological and transcriptomic changes induced by 1 and 4 days of LI (5 µmol photons/m2·s). The results indicated that the inhibition of photomorphogenesis and decreases in photosynthesis and photosynthetic carbon fixation as the duration of LI increased are the key reasons for retarded blade growth under LI conditions. A potential self-amplifying loop involving calcium signaling, phosphatidylinositol signaling, reactive oxygen species signaling, and MAPK signaling may be triggered in blades in response to LI stress. These signaling pathways might activate various downstream responses, including improving light energy use, maintaining cell membrane stability, mitigating oxidative damage, to resist LI stress. Additionally, the LIT strain maintained transcriptional homeostasis better than the LIS strain under LI stress. Specifically, photosynthesis and energy production were relatively stable in the LIT strain, which may help to explain why the LIT strain was more tolerant to LI stress than the LIS strain. The findings of this study provide the basis for future investigations on the precise mechanisms underlying the LI stress tolerance of P. haitanensis.

Construction of a dense genetic linkage map and mapping quantitative trait loci for economic traits of a doubled haploid population of Pyropia haitanensis (Bangiales, Rhodophyta).

BACKGROUND: Pyropia haitanensis is one of the most economically important mariculture crops in China. A high-density genetic map has not been published yet and quantitative trait locus (QTL) mapping has not been undertaken for P. haitanensis because of a lack of sufficient molecular markers. Specific length amplified fragment sequencing (SLAF-seq) was developed recently for large-scale, high resolution de novo marker discovery and genotyping. In this study, SLAF-seq was used to obtain mass length polymorphic markers to construct a high-density genetic map for P. haitanensis. RESULTS: In total, 120.33 Gb of data containing 75.21 M pair-end reads was obtained after sequencing. The average coverage for each SLAF marker was 75.50-fold in the male parent, 74.02-fold in the female parent, and 6.14-fold average in each double haploid individual. In total, 188,982 SLAFs were detected, of which 6731 were length polymorphic SLAFs that could be used to construct a genetic map. The final map included 4550 length polymorphic markers that were combined into 740 bins on five linkage groups, with a length of 874.33 cM and an average distance of 1.18 cM between adjacent bins. This map was used for QTL mapping to identify chromosomal regions associated with six economically important traits: frond length, width, thickness, fresh weight, growth rates of frond length and growth rates of fresh weight. Fifteen QTLs were identified for these traits. The value of phenotypic variance explained by an individual QTL ranged from 9.59 to 16.61 %, and the confidence interval of each QTL ranged from 0.97 cM to 16.51 cM. CONCLUSIONS: The first high-density genetic linkage map for P. haitanensis was constructed, and fifteen QTLs associated with six economically important traits were identified. The results of this study not only provide a platform for gene and QTL fine mapping, map-based gene isolation, and molecular breeding for P. haitanensis, but will also serve as a reference for positioning sequence scaffolds on a physical map and will assist in the process of assembling the P. haitanensis genome sequence. This will have a positive impact on breeding programs that aim to increase the production and quality of P. haitanensis in the future.

Factor analysis of a health-promoting lifestyle profile (HPLP): application to older adults in Mainland China.

UNLABELLED: This research reports preliminary psychometric properties, especially the factor structure, of a Chinese version of a health-promoting lifestyles profile designed for older adults; and examines the distribution of the health-promoting behavioral patterns - both for the purpose of developing culturally sensitive health advancement strategies for Chinese seniors. Responses to this questionnaire were used to measure health-promoting behaviors in a random sample of 1012 elderly Chinese from thirty communities in Xi'an Shaanixi-Province. DESIGN: Factor analysis relied on polychoric correlations with ordinal categorical data were used to evaluate reliability and validity of a revised Chinese version of the health-promoting lifestyles profile (HPLP-C). Because this revised version was used to assess elderly adults, we termed it the HPLP-CE. This factor analysis supported a six-factor model of the original HPLP-C scale. Confirmatory factor analysis indicated a good fit, with factors explaining 88.1% of the common variance of the HPLP-CE scores. Cronbach's α coefficients were 0.91 for the revised instrument, and ranged from 0.67 to 0.88 for six dimensions. The split-half reliability was 0.92, while the test-retest reliability was 0.68. Relationships between HPLP-CE, perceived health status, SF-36 scale scores, and associations with selected demographic variables were significantly positive. CONCLUSIONS: We concluded that this revised scale, based on the 40-item HPLP-C, was considered suitable for measuring health-promoting lifestyles of older adults in China. Mental and inner self-reflection planes were the most salient factors for assessing health-promoting behaviors of seniors. Such factors need to be considered if preventive programs are to be designed to promote seniors' health.