miRNA and Degradome Sequencing Identify miRNAs and Their Target Genes Involved in the Browning Inhibition of Fresh-Cut Apples by Hydrogen Sulfide

Surface browning
is the major limit for the shelf life of fresh-cut
apples, and hydrogen sulfide (H2S) treatment can effectively
inhibit the browning. However, the molecular mechanism on how fresh-cut
apples respond to H2S was poorly understood. MicroRNAs
(miRNAs) are a class of endogenous small noncoding RNAs, which regulate
multiple crucial biological processes in almost all aspects of the
life cycle. Herein, 12 small RNA libraries and one mixed degradome
library were constructed from control and H2S-treated fresh-cut
apples immediately after treatment (C0 and S0) and 6 d of storage
(C6 and S6) at 4 °C. The results identified nine (three upregulated
and six downregulated) and 10 (two upregulated and eight downregulated)
differentially expressed miRNAs (DEmiRNAs) in S0 versus C0 and S6 versus C6, respectively. The target genes
of DEmiRNAs were transcription factors and functional proteins. The
miR156 targeting SPL, miR164 targeting NAC, miR319 targeting TCP4, GAMYB,
and acyl-CoA-binding protein 4, and miR6478 targeting patatin-like protein 2 might play important roles in the
browning inhibition of fresh-cut apples by H2S via regulating
the ROS, phenylpropanoid, and lipid metabolism. The results give valuable
information for further studying the role of miRNA in regulating browning
processes and the underlying molecular mechanism of H2S
treatment on browning inhibition.