Based on citrus transcriptome, how does HSP90s respond under high temperature stress?
Foreword: In recent years, the frequent occurrence of extreme high temperature weather has caused a significant decline in citrus yield and quality, and citrus production has caused a serious negative impact.
How to improve the tolerance of citrus to extreme high temperature and use stress resistance genes to carry out molecularly directed breeding is an effective way to obtain citrus high temperature tolerance germplasm, and the premise and key is to discover and identify important stress resistance genes in citrus and analyze the regulatory network of high temperature stress response.
HSP90 is involved in the response of plants to high temperature stress and is an important candidate gene for genetic improvement of crop heat tolerance.
In this study, six HSP90 gene family members were excavated from the citrus genome.
The number of amino acids in the HSP90 family of citrus was quite different, and the length was between 345~822, and the amino acid numbers of HSP90-3, HSP90-4 and HSP90-6 were 345, 353 and 382, respectively, which were significantly lower than those of the other three.
Gene structure and conserved motif analysis also showed that the number of introns and conserved motifs of HSP90-3, HSP90-4 and HSP90-6 was lower than that of the other 3 genes, which may be due to some evolutionary events that caused incomplete genes or loss of introns.
Phylogenetic analysis showed that most citrus HSP90s and tomato HSP90s were clustered together, and similar amino acid sequences usually had similar biological functions, and citrus HSP90s may have similar response functions to high temperature stress in tomato HSP90s.
HSP90 gene is involved in various biological processes such as plant growth and development regulation and stress response, for example, in wheat, it was found that overexpression of HSP90.2 can enhance the CO2 assimilation ability, grain weight and total yield of transgenic plants.
Based on the published citrus transcriptome data, the expression characteristics of HSP90 in different tissues of citrus were analyzed, and it was found that HSP90 was expressed in leaves, roots, fruits and calli of citrus, indicating that HSP90 was involved in the growth and fruit development process of citrus.
The expression of HSP90 gene was induced by high temperature stress, and the heat shock protein encoded by HSP90 gene could be used as a molecular chaperone to repair the deformed protein, thereby alleviating the damage caused by high temperature to plants.
Four HSP90s were induced by high temperature stress in poplar, seven HSP90s in tomato, seven HSP90s in pepper, and four HSP90s in apple.
Overexpression of GmHsp90A2 and DCHSP90-6 enhanced the heat tolerance of transgenic Arabidopsis thaliana, and the study in pepper also found that the high expression of HSP90 may be the main reason for the heat tolerance of R597 cultivar.
In this study, HSP90-1, HSP90-3, HSP90-4 and HSP90-5 were all induced by high temperature stress in C. chinensis, and their expression levels were significantly higher than those of Mingjian mandarin, indicating that these four genes may be key candidate genes in response to high temperature stress in citrus.
The cis-acting element on the promoter can interact with the trans-acting factor to regulate the expression of genes, and play a key regulatory role in plant growth and stress response.
A large number of abscisic acid, auxin, gibberellin, salicylic acid and methyl jasmonate response elements were found on the promoter of citrus HSP90, suggesting that HSP90 may be regulated by plant hormones.
Abscisic acid in Arabidopsis thaliana and tall fescue can up-regulate the expression of HSFA2c and HSP90 and enhance heat tolerance, and similar results were also found in horticultural crops such as apple, pepper, Chinese cabbage and caryophyllus, indicating that the biological function of HSP90 in different crops is relatively conserved, and all of them are involved in the response to high temperature stress.
Conclusion:
In summary, six HSP90 gene family members were identified from the citrus genome by bioinformatics methods.
Gene expression analysis showed that five HSP90 were induced by high temperature stress in C. chinensis, and the expression levels were significantly higher than those of Mingjian mandarin, suggesting that HSP90-1, HSP90-3, HSP90-4 and HSP90-5 may be the key candidate genes in response to high temperature stress in citrus.
