MicroRNA166-HD-ZIP III module impacts tuber shape, color and productivity in potato

MicroRNA165/166 is a highly conserved and abundant microRNA family in plants that targets class III homeodomain leucine zipper ( HD-ZIP III ) transcription factors. Their essential roles in plant development, organ polarity, meristem maintenance, and vascular differentiation have been well established. However, their role in storage organ development, particularly in potato tuberization remains unknown. Here, we demonstrate the pleiotropic effects of miR166 on potato ( Solanum tuberosum spp. Andigena ) growth and development. Suppression of miR166 via target mimicry (MIM166) resulted in reduced plant height, altered vascular patterning, diminished leaf curvature, and impaired root development. Remarkably, MIM166 lines produced elongated, pigmented tubers with reduced yield under short-day conditions. Transcriptomic analyses of swollen head versus stalk of tuberizing stolons revealed altered expression of auxin-, cytokinin-, and gibberellin-related genes, consistent with hormone quantification data, suggesting the key role of phytohormones in governing tuber shape. Anthocyanin profiling indicated elevated accumulation of cyanidin 3-glucoside, pelargonidin 3-glucoside, and delphinidin 3-glucoside in MIM166 tuber peels, correlating with the upregulation of anthocyanin biosynthetic genes. Tuber productivity in these lines was reduced possibly due to the decreased expression of SWEET11b and distorted vascular structures in the MIM166 lines. Further, StREVOLUTA , a direct miR166 target, exhibited dynamic expression during stolon differentiation and could modulate the expression of auxin biosynthesis genes. Collectively, our results demonstrate that the miR166-HD-ZIP III module is functional in potato, plays conserved roles in regulating key developmental traits, and is active through early stolon-to-tuber transition stages, affecting tuber shape, color and productivity.