Genome-Wide Characterization of the ABA Receptor Pyrabactin Resistance 1-like (PYL) Gene Family in Strawberry and Functional Assessment of FaPYL3 and FaPYL4 in Fruit Ripening

The ABA receptor pyrabactin resistance 1-like (PYR/PYL) protein family is among the key regulators of plant growth and development, participating in ABA signaling. However, information on this family in strawberry (Fragaria × ananassa), an important fleshy fruit crop worldwide, is limited. In the present work, seven homologs of Arabidopsis PYL were first identified and characterized from Fragaria × ananassa. Furthermore, a comprehensive analysis of the FaPYLs was performed, including their phylogenetic relationships, gene structures, chromosomal locations, and conserved domains. The qRT–PCR analysis showed that FaPYL genes had differential expression patterns between fruit ripening stages, and most of them were transcribed in the SG (small green fruits,) and Wh (white fruits) stages of fruit ripening. Treatment of strawberry fruits with ABA and JA changed the expression of all FaPYLs in a gene-specific manner, depending on the berry ripening stage; at the turning stage, only the expression levels of FaPYL3 and FaPYL4 increased in response to ABA. Promoter analysis showed that most FaPYL genes contain cis-acting elements that respond to stress, light, and phytohormones and are associated with tissue-specific expression. Additionally, FaPYL3 and FaPYL4 were further functionally characterized using transient expression technology. Overexpression of FaPYL3 and FaPYL4 promoted strawberry fruit ripening, which positively regulated FaSnRK2.2 and FaNCED1 transcripts. Our results highlight the great potential of FaPYL genes in breeding genetically modified strawberry varieties with accelerated fruit ripening.