On microbial community of Pyropia haitanensis by metagenomic analysis

Microorganisms plays an important role in the growth of Pyropia haitanensis.To understand the structural and functional diversity of the microorganism community of P.haitanensis(PH40),the associated metabolic pathway network in cluster of orthologous groups(COG)and Kyoto Encyclopedia of Genes and Genomes(KEGG),and carbohydrate-active enzymes(CAZymes)were explored in metagenomic analysis.DNA extraction from gametophytes of P.haitanensis was performed first,followed by library construction,sequencing,preprocessing of sequencing data,taxonomy assignment,gene prediction,and functional annotation.The results show that the predominant microorganisms of P.haitanensis were bacteria(98.98%),and the phylum with the highest abundance was Proteobacteria(54.64%),followed by Bacteroidetes(37.92%).Erythrobacter(3.98%)and Hyunsoonleella jejuensis(1.56%)were the genera and species with the highest abundance of bacteria,respectively.The COG annotation demonstrated that genes associated with microbial metabolism was the predominant category.The results of metabolic pathway annotation show that the ABC transport system and two-component system were the main pathways in the microbial community.Plant growth hormone biosynthesis pathway and multi-vitamin biosynthesis functional units(modules)were the other important pathways.The CAZyme annotation revealed that the starch might be an important carbon source for microorganisms.Glycosyl transferase family 2(GT2)and glycosyl transferase family 3(GT3)were the highly abundant families in glucoside transferase superfamily.Six metagenome-assembled genomes containing enzymes involved in the biosynthesis of cobalamin(vitamin B 12)and indole-3-acetic acid were obtained by binning method.They were confirmed to belong to Rhodobacterales and Rhizobiales,respectively.Our findings provide comprehensive insights into the microorganism community of Pyropia.

Quantification of Photosynthetic Pigments in Neopyropia yezoensis Using Hyperspectral Imagery

Phycobilisomes and chlorophyll-a(Chla)play important roles in the photosynthetic physiology of red macroalgae and serve as the primary light-harvesting antennae and reaction center for photosystem Ⅱ.Neopyropia is an economically important red macroalga widely cultivated in East Asian countries.The contents and ratios of 3 main phycobiliproteins and Chla are visible traits to evaluate its commercial quality.The traditional analytical methods used for measuring these components have several limitations.Therefore,a high-throughput,nondestructive,optical method based on hyperspectral imaging technology was developed for phenotyping the pigments phycoerythrin(PE),phycocyanin(PC),allophycocyanin(APC),and Chla in Neopyropia thalli in this study.The average spectra from the region of interest were collected at wavelengths ranging from 400 to 1000 nm using a hyperspectral camera.Following different preprocessing methods,2 machine learning methods,partial least squares regression(PLSR)and support vector machine regression(SVR),were performed to establish the best prediction models for PE,PC,APC,and Chla contents.The prediction results showed that the PLSR model performed the best for PE(R_(Test^(2))=0.96,MAPE=8.31%,RPD=5.21)and the SVR model performed the best for PC(R_(Test^(2))=0.94,MAPE=7.18%,RPD=4.16)and APC(R_(Test^(2))=0.84,MAPE=18.25%,RPD=2.53).Two models(PLSR and SVR)performed almost the same for Chla(PLSR:R_(Test^(2))=0.92,MAPE=12.77%,RPD=3.61;SVR:R_(Test^(2))=0.93,MAPE=13.51%,RPD=3.60).Further validation of the optimal models was performed using field-collected samples,and the result demonstrated satisfactory robustness and accuracy.The distribution of PE,PC,APC,and Chla contents within a thallus was visualized according to the optimal prediction models.The results showed that hyperspectral imaging technology was effective for fast,accurate,and noninvasive phenotyping of the PE,PC,APC,and Chla contents of Neopyropia in situ.This could benefit the efficiency of macroalgae breeding,phenomics research,and other related applications.

Discrepancy in photosynthetic responses of the red alga Pyropia yezoensis to dehydration stresses under exposure to desiccation,high salinity,and high mannitol concentration

Macroalgae that inhabit intertidal zones are exposed to the air for several hours during low tide and must endure desiccation and high variations in temperature, light intensity, and salinity. Pyropia yezoensis (Rhodophyta, Bangiales), a typical intertidal red macroalga that is commercially cultivated in the northwestern Pacific Ocean, was investigated under different dehydration stresses of desiccation, high salinity, and high mannitol concentration. Using chlorophyll fluorescence imaging, photosynthetic activities of P. yezoensis thalli were analyzed using six parameters derived from quenching curves and rapid light curves. A distinct discrepancy was revealed in photosynthetic responses to different dehydration stresses. Dehydration caused by exposure to air resulted in rapid decreases in photosynthetic activities, which were always lower than two other stresses at the same water loss (WL) level. High salinity only reduced photosynthesis significantly at its maximum WL of 40% but maintained a relatively stable maximum quantum yield of photosystem II (PSII) (Fv/Fm). High mannitol concentration induced maximum WL of 20% for a longer time (60 min) than the other two treatments and caused no adverse influences on the six parameters at different WL except for a significant decrease in non-photochemical quenching (NPQ) at 20% WL. Illustrated by chlorophyll fluorescence images, severe spatial heterogeneities were induced by desiccation with lower values in the upper parts than the middle or basal parts of the thalli. The NPQ and rETRmax (maximum relative electron transport rate) demonstrated clear distinctions for evaluating photosynthetic responses, indicating their sensitivity and applicability. The findings of this study indicated that the natural dehydration of exposure to air results in stronger and more heterogeneous effects than those of high salinity or high mannitol concentration.