Genome-wide analysis of the ABC gene family in almond and functional predictions during flower development, freezing stress, and salt stress

ABC (ATP-binding cassette) transporter proteins are one of the most extensive protein families known to date and are ubiquitously found in animals, plants, and microorganisms. ABCs have a variety of functions, such as plant tissue development regulation, hormone transport, and biotic and abiotic stress resistance. However, the gene characterization and function of the ABC gene family in almond (Prunus dulcis) have not been thoroughly studied. In this study, we identified 117 PdABC genes using the whole genome of 'Wanfeng' almond obtained by sequencing and explored their protein characterization. The PdABC family members were classified into eight subfamilies. The members of the same subfamily had conserved motifs but poorly conserved numbers of exons and introns and were unevenly distributed among the eight subfamilies and on the eight chromosomes. Expression patterns showed that PdABC family members were significantly differentially expressed during almond development, dormant freezing stress, and salt stress. We found that PdABC59 and PdABC77 had extremely high expression levels in pollen. PdABC63 and PdABC64 had high expression levels during almond petal development and multiple stages of flower development. PdABC98 was highly expressed in annual dormant branches after six temperature-freezing stress treatments. PdABC29, PdABC69, and PdABC98 were highly expressed under different concentrations of salt stress. This study preliminarily investigated the expression characteristics of ABC genes in different tissues of almond during flower development, freezing stress and salt stress, and the results will provide a reference for further in-depth research and breeding of almond in the future.