Ethylene Signaling Pathway Genes in Strawberry and Their Expression Patterns during Fruit Ripening

Abstract

Ethylene at least partly regulates some aspects during non-climacteric ripening in strawberry. However, the ethylene signaling pathway genes in the strawberry fruit have not been comprehensively and systematically analyzed. In the present study, 15 FaETRs and 14 FaEIN3/EINs were identified in the octoploid strawberry genome. Subcellular localization analysis predicted that FaETRs and FaEIN3/EINs are respectively localized to the endoplasmic reticulum and the nucleus. The phylogenetic trees showed that FaETRs were classified into two subgroups, while FaEIN3/EINs were divided into three clades, which was supported by gene structure and conserved motif analysis. FaETRs and FaEIN3/EINs could interact with several components, such as CTR1, RTE1, EIN2 and ERF1B, in the ethylene signaling pathway by protein–protein interaction network analysis. Transcriptomic data showed that FaETRs were mainly expressed at the early stage of fruit development in three strawberry cultivars. Additionally, a couple of FaETRs (FaETR2 and FaETR13) and FaEINs (FaEIN2 and FaEIN7) could be induced by 1 μM ABA and inhibited by 100 μM nordihydroguaiaretic acid (NDGA, an ABA biosynthesis blocker). These findings suggested that the FaETR- and FaEIN3/EIN-mediated ethylene signaling pathway might play a role in strawberry fruit ripening.