The Effect of Phosphorus Fertilization on Transcriptome Expression Profile during Lentil Pod and Seed Development

Seed coat hardness and water permeability, which are determined by the accumulation of tannins through the phenylpropanoid pathway in the seed, are important lentil quality characteristics. The impact of seeds’ developmental stage and phosphorus (P) fertilization levels on tannin accumulation is still under research. Through RNA sequencing, this study explored the effect of three P treatments (P0, 6 mg kg−1; P1, 15 mg kg−1; and P2, 21 mg kg−1) and three seed maturity stages (S1, immature 2 mm seed in a flat pod; S2, fully developed seed within the pod; and S3, mature seed at the beginning of the pod’s discoloration) on lentil gene expression. The key findings highlighted a significant influence of the seed maturity stage on phenylpropanoid genes, with S1 displaying the highest expression levels, and on phosphorus-related Gene Ontology (GO) terms that presented the highest number of downregulated genes in the S3 to S1 comparison. P exhibited a targeted effect on the flavanone 3-hydroxylase (F3H) and flavonol synthase (FLS) genes and specific gene clusters, as shown by the differential gene expression analysis. This study investigates the molecular mechanisms related to phosphorus fertilization and seed maturity stages that influence tannin accumulation, offering valuable information for the enhancement of lentil product quality through breeding programs.