Screening And Identification Of BZIP Genes Involved In High Light And Stress Tolerance In Gossypium Hirsutum

Cotton is a world economic crop.It is not only the most important fiber crop,but also an important oil crop.With the increase of the global population base,the demand for cotton is also increasing.Because of the change of global climate and the limited area of cultivated land,the stress of high light and drought will cause the reduction of cotton yield.Therefore,it is very important to improve the photosynthetic efficiency of cotton and adapt to the stress for achieveing stable yield and increasing yield of cotton.As an important environmental factor,light plays an important role in seed germination,plant photomorphogenesis,plant flowering and fruit development.However,when the light energy absorbed by the plant exceeds its needed energy,the excess light energy will appear,and the excess light energy will accumulate in the light system,which will lead to the production of various reactive oxygen species,the inhibition of photosynthesis,and even result in the light oxidation and optical destruction.Plants' perception of light is mainly mediated by photoreceptors such as ultraviolet receptor(UVR8),blue light receptor(PHOTs),cryptochrome(CRYs)and phytochrome(PHYs),and the light on growth and development and high light adaptation of plants are mainly mediated by some transcription factors such as PIFs,HY5 and so on.Among them,HY5 and GBF1 bZIPs are the key regulatory elements in the signal pathway.Therefore,bZIPs transcription factors can respond to light,and have important functions in the interaction of light and stress signaling pathways,which can regulate the growth and development of plants in light and the adaptation to adversity.However,the functions of bZIPs transcription factors in regulating the comprehensive adaptation of high light and other stress are not clear in cotton.In fact,cotton has formed its own mechanism in the process of evolution to adapt to stress.In this paper,the bZIP genes of Gossypium hirsutum are mainly studied to reduce the damage of high light and increase the tolerance to stress in plant,which aims to increase the comprehensive adaptation to high light and other adversity in Gossypium hirsutum.Finally,provide the guidance to the high light and stress adaptation in molecular breeding of Gossypium hirsutum.In the first place,this paper systematically analyze the bZIP gene family of Gossypium hirsutum.The chromosome distribution analysis find that the bZIP genes are all almost distributed on each chromosome.The structure of bZIP genes is analyzed by GSDS2.0 online analysis website.Secondly,the bZIP genes,which respond to different light quality and adversity,are screened by RNA-seq in different light quality and stress.26 members are screened from the different light quality transcriptional data and 36 members are screened from the different stress transcriptional data.42 bZIP genes related to high light adaptation and stress tolerance are screened in combination with the promoter component analysis to conduct functional identification.The expression pattern analysis in different light quality treatments shows that the expression of GhbZIP11,GhbZIP53,GhbZIP2,GhbZIP5,GhbZIP29,GhbZIP36,GhbZIP50,GhbZIP58,GhbZIP60 and GhbZIP61 are up-regulated in the low blue light,high blue light,red light and white light,which indicate that the above genes are maybe involved in the light response and light adaptation.The expression pattern analysis in different stress conditions shows that the expression of GhbZIP1,GhbZIP5,GhbZIP29,GhbZIP35,GhbZIP36,GhbZIP41,GhbZIP44,GhbZIP50,GhbZIP51,GhbZIP52 are up-regulated at PEG6000,NaCl,and low temperature,which indicate that the above genes are involved in the stress response and stress adaptation.We analyze the tissue specific expression of genes in response to light and adversity,10 GhbZIP genes are expressing in root,stem,leaf,flower and ovule,and there are different expression in different tissues.GhbZIPl,GhbZIP2,GhbZIPll,GhbZIP44,GhbZIP53,GhbZIP55,GhbZIP58,GhbZIP60,GhbZIP61 are all the highest expression in flower,but GhbZIP42 is the highest expression in stem,which indicate that the bZIP genes are all involved in regulating many biological processes.Finally,we screen the bZIP genes and identify their function in high light adaptation and stress tolerance.The high light adaptation experiments show that over expression of GhbZIP44 does not significantly improve the ability of high light adaptation in transgenic plants,while GhbZIP58 enhances the ability of transgenic plants to adapt to high light adaptation.The maximum photochemical quantum yield(Fv/Fm)of GhbZIP58 overexpressed transgenic plants is higher than the wild type,and its active oxygen scavenging genes are up-regulated expression.The tolerance to salt stress and drought stress in transgenic plants experiments show that the overexpression of GhbZIP55 gene results in the transgenic plants showing a sensitive phenotype to ABA treatment at the stage of seed germination and seedling development.Overexpression of GhbZIP53 and GhbZIP58 enhances the resistance of transgenic plants to salt,ABA and drought.Plant growth experiments show that over expression of GhbZIP53 and GhbZIP58 increase the stress tolerance of transgenic plants in salt and drought environments.The expression analysis of the resistance marker gene show that Some genes,such as GhbZIP58 might enhance the adaptability of plants to light and adversity by regulating reactive oxygen species and ABA synthesis.In summary,we identify the key genes regulating high light adaptation and stress tolerance through screening of bZIP genes related to high light adaptation and stress tolerance in Gossypium hirsutum.The overexpression of GhbZIP58 could help to improve the adaptability of transgenic plants to high light,and the overexpression of GhbZIP53 and GhbZIP58 could help to improve the transgenic plants stress tolerance.The overexpression of GhbZIP55 increases the sensitivity of transgenic plants to ABA.