| Pepper(Capsicum annuum L.), widely cultivated in the world, is an important vegetable crop with high economic value, but it is prone to be damaged by diseases and insects,especially the phytophthora blight caused by Phytophthora capsici. Many chemicals were used to control this disease but it might cause high pesticide reidues in the pepper productions.Therefore, the development of pepper resistant to P. capsici through molecular technique is an important and realistic approach. SQUAMOSA promoter binding protein(SBP)-box genes encode a family of plant-specific transcription factors, which involves extensively in plant growth, development and signal transduction of many physiological and biochemical response. However, the function of the SBP-box family genes is not clear in pepper. Besides,we found a differentially expressed gene(CaSBP05)from the transcriptome databases with the compatible and incompatible Phytophthora capsici based on our lab previous studies. So the SBP-box gene family was analyzed and the two differential expression genes CaSBP11 and CaSBP12 function were also analyzed. we aimed at provide a theoretical basis for the disease resistance to Phytophthora capsici in pepper. The main results of the study are as follows:1. The SBP-box family gene was analyzed using the bioinformatics methods. A total of15 members were identified and they distributed in 7 chromosomes of pepper. Sequence analysis showed that they contain a highly conserved DNA binding domain termed the SBP domain. This domain is an assembly of approximately 76 amino acid residues that are involved in both DNA-binding and nuclear localization, and feaures two zinc-binding sites(C2HC and C3H). Phylogenetic analysis showed that the SBP-box family gene can be divided into 6 groups, and the relationship is close to the dicotyledonous plants. In addition, the homology analysis showed that there were 4 pairs of homologous genes in the pepper genome,and 10 pairs of homologous genes between the Arabidopsis and pepper genome.2. The tissue expression of SBP-box family genes was analyzed. The results showed that the expression patterns of SBP-box gene in different tissues were divided into two types,one is the constitutive expression, and the other was the difference expression. Moreover, thefirst type expression of the genes in the tissues was lower. In general, the expression of SBP-box in the leaves was the highest, followed by the stem and root, and the fruit and flower were the lowest.3. Expression analysis of CaSBP genes under p.capsici and hormone treatments. The results showed that seven members of CaSBP genes(CaSBP01, 02, 04, 05, 06, 11, 12 and 13)were up-regulated after the compatible strains or incompatible strains P.capsici inoculation,while CaSBP07, 09, 10, 14 and 15 were down-regulated. Moreover, CaSBP03 and 08 were up-regulated after compatible P.capsici inoculation, down-regulated after incompatible p.capsici inoculation. The result showed that the expression of these genes was rapidly down regulated after the SA biosynthetic inhibitor(PBZ) and MeJA biosynthetic inhibitor(SHAM)treatment, and reached the lowest at 6 h. After MeJA treatment, the peak value of these genes expression appeared earlier than that after SA treatment.4. Two differentially expressed genes(CaSBP11 and CaSBP12) after p.capsici inoculation were screened and charactered using the virus induced gene silencing(VIGS)technique. There was no obvious phenotypic difference between the silence plants and control plants. Besides, the silence efficiency of the silence plants reached 60%. The resistance and root activity of the silence plants were enhanced, which indicated that CaSBP11 and CaSBP12 genes may play a negative role in the resistance of pepper to p.capsici inoculation.In addition, salt stress of the silent plants showed that the two genes may be play a positively regulation role in the process of salt stress. |
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