Single-nucleus RNA sequencing and mRNA hybridization indicate key bud events and LcFT1 and LcTFL1-2 mRNA transportability during floral transition in litchi

Single-nucleus RNA sequencing of litchi apical buds combined with mRNA hybridization signatures identified key genes involved in floral initiation, and indicated that FTand TFL1mRNA are transportable. In flowering plants, floral induction signals intersect at the shoot apex to modulate meristem determinacy and growth form. Here, we report a single-nucleus RNA sequence analysis of litchi apical buds at different developmental stages. A total of 41 641 nuclei expressing 21 402 genes were analyzed, revealing 35 cell clusters corresponding to 12 broad populations. We identify genes associated with floral transition and propose a model that profiles the key events associated with litchi floral meristem identity by analyzing 567 identified floral meristem cells at single cell resolution. Interestingly, single-nucleus RNA-sequencing data indicated that all putative FT and TFL1 genes were not expressed in bud nuclei, but significant expression was detected in bud samples by RT-PCR. Based on the expression patterns and gene silencing results, we highlight the critical role of LcTFL1-2 in inhibiting flowering and propose that the LcFT1/LcTFL1-2 expression ratio may determine the success of floral transition. In addition, the transport of LcFT1 and LcTFL1-2 mRNA from the leaf to the shoot apical meristem is proposed based on in situ and dot-blot hybridization results. These findings allow a more comprehensive understanding of the molecular events during the litchi floral transition, as well as the identification of new regulators.

Automated summary

Single-nucleus RNA sequencing combined with mRNA hybridization identified key genes involved in floral initiation in litchi apical buds. The analysis of 41,641 nuclei revealed 35 cell clusters and proposed a model profiling the key events associated with litchi floral meristem identity. Interestingly, the transportability of FT and TFL1 mRNA from leaf to shoot apical meristem was proposed based on hybridization results. These findings provide insights into the molecular events during litchi floral transition and the identification of new regulators.