Abstract
Abstract
Gibberellic acid (GA) and abscisic acid (ABA) antagonistically regulate various biological processes, but whether they antagonistically regulate tissue browning remains unclear. Here, we showed that ABA reduced pineapple internal browning (IB) by inhibiting phenolic biosynthesis via downregulating AcWRKY75 and AcMYB108, while GA
3
had the opposite effects. Biochemical evidences showed AcWRKY75 and AcMYB108 directly bound to and activated the phenolic biosynthetic gene
Ac4CL5
. Interestingly, AcMYB108 directly bound to
AcWRKY75
promoter and activated its transcription, indicating that AcMYB108 functions upstream of
AcWRKY75. Arabidopsis
overexpressing
AcWRKY75
,
AcMYB108
or
Ac4CL5
displayed promoted phenolic biosynthesis.
AcWRKY75
transient overexpression in pineapple reduced, while its transient silencing enhanced IB and phenolic accumulation. Transcriptomic profiling of pineapples transiently overexpressing and silencing
AcWRKY75
revealed that plant hormone signal transduction and phenylpropanoid biosynthesis were among the most significantly enriched KEGG pathways, suggesting the role of AcWRKY75 in regulating phenolic biosynthesis involves plant hormones. ABA suppressed and GA
3
enhanced enzyme activity of GUS transiently expressed in tobacco driven by promoter of
AcWRKY75
,
AcMYB108
or
Ac4CL5
. This work suggests that WRKY75 and MYB108 are involved in antagonism between ABA and GA in regulating IB, and may shed novel insight into the role of ABA and GA in regulating plant tissue browning.