| Lichuan of Hubei province is one of the four producing areas of Brasenia schreberi,Due to the colder and longer winters in the region,as the temperature drops,Brasenia schreberi can form dormant shoots,resulting in a shorter picking period,which in turn affects the overall yield of Brasenia schreberi,and low temperatures can easily damage Brasenia schreberi,affecting its growth and quality,thus limiting the cultivation of Brasenia schreberi.Therefore,the selection of cold-resistant Brasenia schreberi resources with excellent varietal characteristics and research on their cold resistance are of great practical importance for the selection and breeding of cold-tolerant Brasenia schreberi resources and for production practice.In this experiment,leaves of Brasenia schreberi Li Chuan(LC),Brasenia schreberi Hangzhou(HZ)and a new strain of Brasenia schreberi(BXM)were used as materials.By measuring cold resistance indices and analysing their relationship to,Evaluation of the characteristics of Brasenia schreberi.in combination with production performance and quality evaluation indicators,and selection of high-quality,cold-resistant resources of Brasenia schreberi.The selected cold-resistant germplasm was subjected to transcriptomic analysis to preliminarily investigate the molecular mechanisms of cold resistance in Brasenia schreberi.The results of the study are as follows:(1)As the treatment temperature decreased,the soluble sugar(SS)content of the three kinds of Brasenia schreberi resources showed a trend of increasing and then decreasing.LC,BXM and HZ reach their peak value under 0 ℃,5 ℃ and 10 ℃stress,which is significantly increased by 29.4%,75.6 % and 16.3% compared with the control,respectively.The content of soluble protein(SP)showed a slow increasing trend.The content of LC and BXM reached the peak at-5 ℃,which was significantly increased by 5.7 % and 10.4 % compared with the control,respectively.The content of LC and BXM was the highest at 0 ℃,which was significantly increased by 6.8 % compared with the control.The content of malondialdehyde(MDA)increased first and then decreased,in which the MDA content of LC was the highest,followed by HZ and BXM,indicating that the damage degree of LC film was the most serious.The activity of superoxide dismutase(SOD)increases and catalase(CAT)increases first and then decreases.It can be seen from the activity analysis that the activities of BXM and HZ are higher than LC.The POD activity of LC was higher than that of BXM and HZ.Based on the analysis of the above indexes combined with the membership function,it is obtained that the ability of B Brasenia schreberi from strong to weak is BXM > HZ > LC.(2)In all three portions of Brasenia schreberi,the shoot/leaf dry matter content and shoot weight of HZ were higher than those of BXM and LC;The content of ascorbic acid As A(VC)in HZ was the highest(66.6mg /g),followed by BXM and LC was the lowest.The relative water content(RWC)of LC was the highest(92%),and the RWC content of BXM was the lowest(85.9%),which was significantly lower than that of HZ and LC.The chlorophyll content from high to low was HZ > BXM >LC.(3)The relative electrical conductivity(REC)of the three Brasenia schreberi species showed an increasing trend,with LC having the highest REC(88.05 %)and BXM having the lowest REC(73.65 %).According to the fitting of electrical conductivity and Logistic equation,the LT50 of LC,HZ and BXM are-1.69 ℃,-2.73 ℃ and-3.04 ℃ respectively,which is consistent with the analysis result of membership function method.Their cold resistance in order of strength BXM > HZ >LC.(4)The leaves of BXM a variety with high cold resistance,and LC a variety with low cold resistance,,were treated at-5 ℃ with normal temperature as the control.A total of 79.58 Gb of Clean Data were obtained by transcriptic sequencing,and the percentage of Q30 bases was 94.76%.Its N50 is 1,464,its total length is 84,518,449,and its average length is 846.02.Compared with KOG,KEGG and GO databases,the proportions of annotations between LC(BXM)control and treatment groups were51%(51.2 %),63.52 %(63.53 %)and 78.28 %(77.2 %),respectively.The intergroup annotation ratio of LC and BXM were 40.58 %,67.39 % and 79.71 %,respectively.Compared with the control,BXM treated at-5 ℃ produced 7,558 differential genes,among which 2,821 were up-regulated and 4,737 were down-regulated;LC treated at-5 ℃ produced 6,583 differential genes,among which 2,392 were up-regulated and 4,191 were down-regulated.The total number of differential genes and the number of up-down-regulated genes in BXM were more than those in LC.(5)GO taxonomic enrichment analysis showed that the LC and BXM differential gene enrichment types were mainly: Protein complexes,biological regulation,cell process,substance collection,transcription regulation,antioxidant activity,transport and metabolism are damaged after treatment at low temperature.Protein changes and POD active genes are enriched when Brasenia schreberi resizes adversity.The main pathways of KEGG enrichment analysis include amino acid biosynthesis,phenylpropanoid compound synthesis,flavonoid biosynthesis,starch and sucrose metabolism,and plant hormone signal transduction.Under low temperature stress,osmotic pressure is regulated by amino acid accumulation.Flavonoid biosynthesis pathway can reduce the damage of ROs-shield to water shield,and sugar metabolism responds to low temperature stress.It plays the role of signal transduction and regulation,and is closely related to the cold resistance of Brasenia schreberi.(6)According to transcription factor prediction analysis,among 113down-regulated genes in BD vs BS and 126 down-regulated genes in LD vs LS,AP2/ERF family gene expression was relatively high;The transcription factors in LS vs DS are mainly concentrated in MYB-related family genes.These genes can enhance plant stress resistance,indicating that the transcription factors play an active role in gene expression when Brasenia schreberi is responsive to low temperature stress. |
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