Preliminary Research On Response Mechanism Of Porphyra Haitanensis Under High-temperature Stress

This response characteristics of gametophytic blades of two high temperature-tolerancelines (Z-61, Z-26) and a wild-type line of Porphyra haitanensis under high temperature stresswere studied from growth characteristics, quality parameters, physiological indexes and thedifferential gene expression:1．Growth characteristics: Under two high temperatures(30℃,26℃) stress, the blade colourof Z-61and Z-26was faded gradually, but they could restore to normal growth state whenremoved to culture under normal temperature for some days. However, the cytoplasm ofwild-type line leaked out and necrosis gradually after cultured under30℃for two days, andfather, they could not restore to normal growth state when removed to culture under normaltemperature.2．Quality parameters:5quality parameters (included the contents of phycobiliprotein,Chlorophyll a, crude protein, total amino acids and free amino acids) were detemined. Theresults showed that all the5quality parameters of Z-61, Z-26and wildtype line were nosignificantly changes under21℃, but significantly or highly significantly declined(P<0.05orP<0.01) under26℃and30℃. The declined amplitude of Z-61and Z-26is smaller than thewild-type line.3．Physiological indexes: several physiological indexes (included the contents of freeradical, hydrogen peroxide (H2O2), malondialdehyde (MDA), proline (Pro) and the activity ofsuperoxide dismutase (SOD) and peroxidase (POD), and catalase(CAT)) were determined. Theresults showed that all these indexes were presented as dynamic changes on the stress days. Sobased on these data, we concluded the physiological process of the gametophytic blades of Z-61and Z-26response to high temperature stress was: high temperature stress→levels of reactiveoxygen species(ROS) increased→cell membranes were damaged by oxidation and MDA levelsincreased→cells received signals of excessive ROS→antioxidation and osmoregulation systemsbegan to clean out excessive ROS→free radical levels declined. By comparing the responsesmechanism of high temperature-tolerance lines and wild-type lines to high temperature stress, weknowed that the high temperature-tolerance lines can initiate both antioxidation andosmoregulation systems to resist to stress, but the wild-type line only can initiate osmoregulationsystem.4. Differential gene expression: The ACP technology was used to investigate the genes ofZ-61which differential expressed under high temperature stress for0days and6days,6gene fragments which senquence length each was387bp(GW-1),512bp(GW-2),702bp(GW-3),360bp(GW-4),228bp(GW-5) and132bp(GW-6) were gained. Furthermore, relative expressivelevel of gene GW-1, GW-2, GW-3, GW-4and GW-5on the blades of Z-61which cultured underhigh temperature stress for0,2,4,6,8,10days were also determined by qPCR, respectively, theresults showed that the expressive level of each gene was significantly changed on the differentstress days. Protiens which encoded by these genes were relative with signal transduction,protein supersession and others by analyzing with blast-x.5. A full length cDNA sequence of702bp(GW-3) was obtained and was assigned to a newNCBI accession number JF719273. It encoded a protein which included195amino acids,theoretical isoelectric points was9.99, instability index was37.43, coefficient of fat was88.00,the proportions of amino acids which was constructed helix, pleated sheet and loop were38.46%,21.54%and40.00%, respectively.