Genome-wide Identification, Phylogenetic Evolution And Expression Analysis Of CCO And GATA Gene Families In Apple

Carotenoid cleavage oxygenases(CCOs)are able to cleave carotenoids to produce apocarotenoids and their derivatives,which are important for plant growth and development.Plant GATA transcription factors are type-IV zinc-finger proteins that also play important regulatory roles in plant growth and development.They are known for their specific binding of the consensus sequence WGATAR(W=T or A;R=G or A).The CCO and GATA gene families play an important role in plant stress response.Despite efforts made to investigate the CCO and GATA gene family in model plants such as Arabidopsis.thaliana and O.sativa,these families are relatively uncharacterized in apple.In this study,we therefore performed a genome-wide search for CCO and GATA genes in the apple genome and analyzed their chromosomal distributions,evolutionary mechanisms,gene structures,functional domains,and cis-elements.Using microarray gene expression data and qRT-PCR technology,we systematically analyzed the expression patterns of CCO and GATA genes in different organs of apple,and the changes in some physiological indicators of apple under dark,drought,and salt stress conditions were identified.Then we analyzed the expression patterns of apple GATA genes under dark stress,apple CCO genes under drought and salt stress as well as various phytohormone treatments in order to identify apple CCO and GATA genes related to abiotic stress response.The result is as follows:1.Identification of CCO and GATA genes in apple.21 and 35 members of the CCO and GATA gene family were identified separately in apple.Our analysis indicated that the instability index indexes of most MdGATA proteins are above 40,suggesting their possible instability.2.Evolution analysis of CCO and GATA genes.According to the phylogenetic relationships,the CCO and GATA genes were divided into six and four groups,respectively.An analysis of the synteny within the apple genome revealed that tandem,segmental,and whole-genome duplication events likely contributed to the expansion of the apple carotenoid oxygenase gene family.10 pairs of putative MdGATA paralogs were also identified,and they have mainly undergone whole genome duplication.24 and 18 orthologous CCO and GATA gene pairs were also identified between A.thaliana and apple,respectively,which served as references for the functional analysis of apple CCO and GATA genes.3.MdCCO and MdGATA gene expression patterns in different tissues.Apple CCO and GATA genes exhibit diverse temporal and spatial expression patterns in different tissues,showing that these genes may exert diverse functions at different development stages of different tissues.4.Apple CCO genes responds to different hormone treatments.The expression of most MdCCO genes can be significantly induced by different hormone treatments,implicating that they may be involved in hormone-mediated apple growth or response to various abiotic stresses.5.Analysis of physiological responses as well as CCO and GATA gene expression patterns in apple under various abiotic stresses.Apple tissue culture seedlings maintained in darkness for 7 days exhibited a moderate decline in chlorophyll content.The net photosynthetic rate,transpiration rate,and stomatal conductance of potted seedlings leaves decreased,while leaf stomatal density increased under drought and saline conditions.Under dark stress,the expression of MdGATA7、MdGATA18、MdGATA32 and MdGATA34 were significantly induced.Under drought and salt stresses,the expression levels of MdCCD7 b and MdCCD-like-c also significantly increased,indicating that these genes play an important role in apple stress resistance.