1. A molecular marker for chicken infected with Campylobacter jejuni is characterized in that the nucleotide sequence of the molecular marker is shown in SEQ ID NO. 1.

2. A method for detecting chicken infected with campylobacter jejuni is characterized by comprising the following steps:

1) extracting chicken cecum tissue total RNA, and carrying out reverse transcription;

2) taking the reverse transcription DNA as a template, and respectively utilizing a detection primer and an internal reference primer to carry out PCR amplification; wherein the detection primers are shown as SEQ ID NO. 4-5, and the internal reference primers are shown as SEQ ID NO. 6-7;

3) use after internal reference correction 2^-△△CtThe method calculates the difference multiple of the chicken to be detected and the negative chicken isomiR-1, and the chicken isomiR-1 with the expression quantity more than 6 times of the negative chicken is judged as the positive chicken of the campylobacter jejuni.

3. The method for detecting the campylobacter jejuni infection of chickens according to claim 2, wherein the reverse transcription primer nucleotide sequence is shown as SEQ ID No. 3.

4. The method for detecting the infection of the chicken with the campylobacter jejuni according to claim 2, wherein the PCR system comprises: 2 XChamQ Universal SYBR qPCR Master Mix 10.0. mu.l, upstream and downstream primers 0.4. mu.l each, Template DNA 2.0. mu.l, ddH₂O 7.2μl。

5. The method for detecting the infection of the chicken with the Campylobacter jejuni according to claim 4, wherein the PCR program is: pre-denaturation at 95 ℃ for 30 sec; 10sec at 95 ℃, 30sec at 60 ℃, 40 cycles; 95 ℃ for 10sec, 65 ℃ for 60sec, 97 ℃ for 1 sec.

6. A primer for detecting chicken infected with campylobacter jejuni is characterized by being shown in SEQ ID No. 4-5.

7. Use of the molecular marker of claim 1 or the primer of claim 6 for detecting infection of Campylobacter jejuni in chickens.

Background

Campylobacter jejuni (C.jejuni) is a gram-negative bacterium, microaerophilic (5% oxygen, 10% carbon dioxide, 85% nitrogen) is a species of Campylobacter, chickens are the main hosts of Campylobacter jejuni, can cause the morbidity of livestock and poultry, cause serious economic loss in animal husbandry, are also one of the main pathogenic bacteria of human foodborneal diseases, and are a zoonotic pathogenic bacterium.

microRNA (miRNA) is short, single-stranded and non-coding RNA, has the length of about 20-24 nt, and is widely present in animals, plants and viruses. The same miRNA precursor can form a plurality of miRNAs isomers-isomiR with different lengths or sequences due to various reasons of Drosha or Dicer shearing site change, exonuclease mediated miRNA end shortening, miRNA editing and the like. Enables more fine-grained regulation of gene expression at the post-transcriptional level. Because the isomiR and an annotation thereof usually have only a few base differences, the existing tailing method and stem-loop method for detecting miRNA are unable to distinguish the differences well, which causes great difficulty for the detection of isomiR and the application in breeding for disease resistance.

Earlier researches find that after chicken is infected with campylobacter jejuni, one isomer isomiR-1 of gga-miR-24-3p is obviously up-regulated, and the basal expression level is higher than that of other isomers, so that the chicken is suitable to be used as an endogenous biomarker. The method is a novel molecular marking method, can overcome the defects that the traditional microorganism detection method is low in sensitivity and difficult to determine whether endogenous pollution exists, can quickly and efficiently monitor the infection condition of the campylobacter jejuni, is suitable for poultry genetic breeding research, and has potential application value in the field of disease-resistant breeding.

Disclosure of Invention

The invention aims to provide a molecular marker for detecting chicken infected with campylobacter jejuni, which is used for determining whether the chicken is infected with campylobacter jejuni or not by detecting the expression level of a specific gga-miR-24-3p isomer isomiR-1 in chicken cecal tissues, and has potential application value in the field of poultry disease-resistant breeding.

In order to achieve the technical purpose, the invention specifically adopts the following technical scheme:

a molecular marker of chicken infected campylobacter jejuni is isomer isomiR-1 of chicken cecal tissue gga-miR-24-3p, and the nucleotide sequence of the molecular marker is shown in SEQ ID NO. 1.

The nucleotide sequence of the gga-miR-24-3p is shown in SEQ ID NO. 2.

In another aspect of the present invention, there is provided a method for detecting infection of chicken with Campylobacter jejuni, comprising the steps of:

1) extracting chicken cecum tissue total RNA, and carrying out reverse transcription;

2) taking the reverse transcription DNA as a template, and respectively utilizing a detection primer and an internal reference primer to carry out PCR amplification;

3) after internal reference correctionThe method calculates the difference multiple of the chicken to be detected and the negative chicken isomiR-1, and the chicken isomiR-1 with the expression quantity more than 6 times of the negative chicken is judged as the positive chicken of the campylobacter jejuni.

Further, the reverse transcription primer nucleotide sequence is shown as SEQ ID NO. 3.

Further, the detection primers are shown as SEQ ID NO. 4-5, and the internal reference primers are shown as SEQ ID NO. 6-7.

Further, the PCR system is as follows: 2 XChamQ Universal SYBR qPCR Master Mix 10.0. mu.l, upstream and downstream primers 0.4. mu.l each, Template DNA 2.0. mu.l, ddH₂O 7.2μl。

Further, the PCR procedure is: pre-denaturation at 95 ℃ for 30 sec; 10sec at 95 ℃, 30sec at 60 ℃, 40 cycles; 95 ℃ for 10sec, 65 ℃ for 60sec, 97 ℃ for 1 sec.

In another aspect of the invention, the detection primer is also within the protection scope of the invention, and the primer can detect chicken cecal tissue gga-miR-24-3p isomer isomiR-1.

In another aspect of the invention, the application of the molecular marker or the detection primer in detecting the chicken infected with campylobacter jejuni is also provided. And (3) determining that the expression quantity of the isomiR-1 of the chicken to be detected exceeds more than 6 times of that of the negative chicken by real-time fluorescent quantitative PCR (polymerase chain reaction).

The invention has the beneficial effects that:

the expression level of the screened gga-miR-24-3p isomer isomiR-1 is closely related to chicken infected campylobacter jejuni, and is a new endogenous biomarker. The method is a novel molecular marking method for determining whether chicken cecal tissue gga-miR-24-3p isomer isomiR-1 is infected with campylobacter jejuni or not by detecting the expression level of the chicken cecal tissue gga-miR-24-3p isomer isomiR-1.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The embodiment provides a molecular marker method for determining whether chickens are infected with campylobacter jejuni by detecting the expression level of specific gga-miR-24-3p isomer isomiR-1 in cecum tissues of the chickens, and the molecular marker method has potential application value in the aspect of poultry disease-resistant breeding. The specific contents are as follows:

1) RNA extraction and reverse transcription

Extracting the total RNA of the chicken cecal tissues by adopting a Trizol method, and carrying out reverse transcription by utilizing the stem-loop primers shown in the table 1, the reagent preparation methods shown in the tables 2 and 3 and reaction conditions. The stem-loop primer can specifically recognize 6 bases at the 3' end of isomiR-1 (the internal reference is U6 which is stably expressed in cells). By verification, the primers, isomiR-1 and U6 can respectively and specifically amplify target PCR products, and subsequent quantitative work can be carried out.

Table 1 related primers for detecting gga-miR-24-3p isomer isomiR-1

TABLE 2 reverse transcription reaction mixtures

TABLE 3 reverse transcription reaction conditions

2) Quantitative PCR

The above-mentioned reverse-transcribed DNA was used as a template, and the upstream and downstream primers shown in Table 1 were used to perform quantitative PCR, the reaction mixture and the reaction conditions are shown in tables 4 and 5, respectively, and the quantitative PCR apparatus was Roche96。

TABLE 4 qPCR reaction mixture

TABLE 5 qPCR reaction conditions

3) Calculation of IsomiR-1 expression level and determination of Campylobacter jejuni-positive chickens

According to Ct values of the chicken to be detected and the campylobacter jejuni negative chicken isomiR-1 detected by qPCR, correcting the Ct values by using internal reference and then using the corrected Ct valuesThe method calculates the difference multiple of two isomiR-1, and the chicken to be detected is judged to be the positive chicken of campylobacter jejuni if the expression quantity of the isomiR-1 exceeds more than 6 times of the negative chicken.

Example 2

In this embodiment, the detection method of the gga-miR-24-3p isomer isomiR-1 is verified by a sequencing method, and the detection method comprises the following steps:

1) randomly dividing 30 Campylobacter jejuni negative chickens into a test group and a control group, and irrigating each chicken in the test group with 0.5ml of Campylobacter jejuni bacterial liquid (1 × 10)⁸cfu/ml), control groups were infused with equal volumes of PBS, and then both groups of chickens were housed in separate isolators with free access to food and water to avoid cross-contamination.

2) At 8h after inoculation, 10 chickens were randomly selected from each of the test group and the control group, and cecal tissues and cecal contents were taken after euthanasia. And (4) preserving the caecum tissues in liquid nitrogen, and preserving the caecum contents at a low temperature of 0-4 ℃.

3) Determining the content of campylobacter jejuni in the cecal content sample to confirm that the artificial infection model is successfully constructed; then, a certain number of cecal tissue samples are respectively selected from the control group and the test group and sent to a sequencing company for transcriptome sequencing.

4) After sequencing data are obtained, an isomer isomiR-1 of the gga-miR-24-3p is screened out through quality control, splicing and comparison, and the ratio of positive chickens and negative chickens of the campylobacter jejuni is 5.75, which shows that the isomer isomiR-1 of the gga-miR-24-3p is closely related to campylobacter jejuni infection.

5) By adopting the detection method disclosed by the invention, a fluorescence quantitative result is obtained through RT-qPCR, the ratio of positive chicken and negative chicken of campylobacter jejuni is 6.34, and is very close to a sequencing result of 5.75, so that the detection method disclosed by the invention can be used for accurately detecting and quantifying isomer isomiR-1 of gga-miR-24-3p, and has potential application value in poultry breeding for disease resistance.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

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