GhmiR858 Inhibits the Accumulation of Proanthocyanidins by Targeting GhTT2L in Cotton (Gossypium hirsutum)

Proanthocyanidins (PAs) are predominantly regulated at the transcriptional level by sophisticated regulatory networks. In cotton, the role of miRNAs as key regulatory factors at the post-transcriptional level is still unclear. Here, we demonstrated that GhmiR858 negatively regulates PA accumulation in cotton leaves and calli by targeting GhTT2L. Excessive expression of GhmiR858 restrained the expression of GhTT2L, resulting in a significant decrease in PA abundance. Conversely, a reduction in GhmiR858 activity upregulated GhTT2L, which increased PA accumulation. Additionally, GhTT2L was found to positively regulate PA accumulation in both cotton and Arabidopsis. Further analyses showed that GhTT2L interacted with transcription factor GhTTG1, which directly binds to the GhANR promoter, to facilitate its transcription. This study provides new information to guide future studies of the PA regulatory mechanisms affected by miRNAs as well as the breeding of novel varieties of colored cotton with rich PAs.