Abstract
Overcoming short-day-dependent tuberization to adapt to long-day conditions is critical for the widespread geographical success of potato. The genetic pathways of photoperiodic tuberization are similar to those of photoperiodic flowering. DNA methylation plays an important role in photoperiodic flowering. However, little is known about how DNA methylation affects photoperiodic tuberization in potato. Here, we verified the effect of a DNA methylation inhibitor on photoperiodic tuberization and compared the DNA methylation levels and differentially methylated genes (DMGs) in the photoperiodic tuberization process between photoperiod-sensitive and photoperiod-insensitive genotypes, aiming to dissect the role of DNA methylation in the photoperiodic tuberization of potato. We found that a DNA methylation inhibitor could promote tuber initiation in strict short-day genotypes. Whole-genome DNA methylation sequencing showed that the photoperiod-sensitive and photoperiod-insensitive genotypes had distinct DNA methylation modes in which few differentially methylated genes were shared. Transcriptome analysis confirmed that the DNA methylation inhibitor regulated the expression of the key genes involved in the photoperiod and GA pathways to promote tuber initiation in the photoperiod-sensitive genotype. Comparison of the DNA methylation levels and transcriptome levels identified 52 candidate genes regulated by DNA methylation that were predicted to be involved in photoperiodic tuberization. Our findings provide a new perspective for understanding the relationship between photoperiod-dependent and GA-regulated tuberization. Uncovering the epigenomic signatures of these pathways will greatly enhance potato breeding for adaptation to a wide range of environments.
Highlights
Potato (Solanum tuberosum L.) originated in the SouthAmerican Andes and has been the main food consumed by the local population for over 8000 years[1]
The expression of the genes involved in the CO-FT pathway in the treatment and control groups for the above three genotypes grown under short-day induced (SD) conditions for 28 days confirmed that the tuberization marker gene StSP6A was significantly upregulated in the E26 treatment group compared to the control, but it was downregulated in E108 and nearly not expressed in E20 (Fig. 1c)
These results indicated that DNA methylation inhibitors promoted tuber initiation in strict short-day genotypes by regulating the photoperiodic tuberization pathway
Summary
Potato (Solanum tuberosum L.) originated in the SouthAmerican Andes and has been the main food consumed by the local population for over 8000 years[1]. The day length is perceived by the photoreceptor in leaves, and the signal is transported to underground stolons to induce tuber initiation[5]. Phytochromes are the main photoreceptors for day-length sensing, and phytochromes B and F play key roles in photoperiodic tuberization control by regulating the CO-FT pathway[7,8]. StSP6A, an FT homolog, has been identified to be a tuberigen that can be transported from leaves to stolons to induce tuber initiation[9]. Another FT homolog, StSP5G, acts as a repressor of tuberization by repressing the expression of StSP6A under long-day (LD) conditions[7]
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