Improved Longan Genome Assembly Reveals Insights Into Flowering Mechanisms.

Area of Science:

• Plant Biology
• Genomics
• Agricultural Science

Background:

• Longan (Dimocarpus longan Lour.) is a tropical fruit crop.
• Off-season flowering can be induced using potassium chlorate (KClO₃).
• The molecular mechanisms underlying KClO₃-induced flowering are not well understood.

Purpose of the Study:

• To elucidate the molecular mechanisms of KClO₃-induced flowering in longan.
• To assemble and analyze the longan genome.
• To compare flowering pathways in natural and induced flowering.

Main Methods:

• Genome sequencing and assembly of the longan variety 'Shixia'.
• Comparative genomics with lychee.
• Transcriptomic profiling of longan under different flowering conditions.
• Gene expression analysis in Arabidopsis.

Main Results:

• A high-quality longan genome was assembled.
• KClO₃-induced flowering involves gibberellin and autonomous pathways, repressing DlDDF1.
• Perpetual flowering in 'Sijimi' is linked to photoperiod gene expression.
• DlDDF1 overexpression delays flowering, partially reversed by KClO₃.

Conclusions:

• KClO₃-induced longan flowering is mediated by oxidative stress and gibberellin signaling via DlDDF1 repression.
• Natural flowering is regulated by seasonal cues.
• These findings provide a basis for genetic improvement of longan flowering.