Identification of pathways and lncRNAs involved in date palm flowering using RNA-Seq technique

The date palm, known scientifically as Phoenix dactylifera L, grows well in tropical and subtropical regions. The process of flower development initiates sexual reproduction in plants. Specific genes regulate this process in the floral meristem, cycle, organ identity, and certain lncRNAs. Studies on animals have shown that lncRNAs are notably active in reproductive organs.

We aimed to explore the pathways and lncRNAs involved in date palm flowering. Minab date palm flower bud samples were collected from the Tropical Fruit Research Station in Hormozgan Province, Iran. The samples were then transferred to the Tabaristan Agricultural Biotechnology Research Institute for analysis. RNA was extracted from various cultivars' male and female flower buds and combined equally. Two replicates were produced for each mixed sample. Subsequently, it was sent for sequencing.

We scrutinized the sequencing outcomes to delve into the mechanisms of plant flowering which is dependent on seasonal cues and is influenced by environmental factors and specific genes. Our research focused on four key pathways: photoperiod, vernalization, self-stimulation, and gibberellin. Our investigation uncovered long non-coding RNAs (lncRNAs) associated with date palm flowering. We identified 13 lncRNAs in the photoperiod pathway, one in the self-stimulation, and four in the gibberellin pathway. Interestingly, no lncRNAs were detected in the vernalization pathway. We proceeded to compare these lncRNAs with those found in other plant species. The lncRNAs in the photoperiod pathway resembled those in oil palm, red clover, olive, and wheat. Their increased expression leads to accelerated flowering, irrespective of photoperiod. Moreover, we pinpointed a lncRNA in the gibberellin pathway that is similar to the one found in cotton which is linked to the LFY gene. Furthermore, our study revealed four lncRNAs in the self-stimulation pathway, resembling lncRNAs in apple, millet, and pea, all of which are associated with the FCA gene.

The flowering process in plants occurs only in certain seasons of the year, through regulatory networks resulting from environmental signals and involving the genes associated with the four regulatory pathways of flowering: photoperiod, vernalization, self-stimulation, and gibberellin. The identification and comparison of lncRNAs involved in different flowering pathways, along with the identification of related genes, provide the basis for future applied research in this valuable plant.