Transcriptome and Metabolome Based Mechanisms Revealing the Accumulation and Transformation of Sugars and Fats in Pinus armandii Seed Kernels during the Harvesting Period

Pinus armandii seed kernel
is a
nutrient-rich and widely consumed nut whose yield and quality are
affected by, among other things, harvesting time and climatic conditions,
which reduce economic benefits. To investigate the optimal harvesting
period of P. armandii seed kernels,
this study determined the nutrient composition and seed kernel morphology
and analyzed the gene expression and metabolic differences of P. armandii seed kernels during the harvesting period
by transcriptomics and metabolomics. The results revealed that during
the maturation of P. armandii seed
kernels, there was a significant increase in the width, thickness,
and weight of the seed kernels, as well as a significant accumulation
of sucrose, soluble sugars, proteins, starch, flavonoids, and polyphenols
and a significant decrease in lipid content. In addition, transcriptomic
and metabolomic analyses of P. armandii seed kernels during the harvesting period screened and identified
103 differential metabolites (DEMs) and 8899 differential genes (DEGs).
Analysis of these DEMs and DEGs revealed that P. armandii seed kernel harvesting exhibited gene–metabolite differences
in sugar- and lipid-related pathways. Among them, starch and sucrose
metabolism, glycolysis, and gluconeogenesis were associated with the
synthesis and catabolism of sugars, whereas fatty acid degradation,
glyoxylate and dicarboxylic acid metabolism, and glycerophospholipid
metabolism were associated with the synthesis and catabolism of lipids.
Therefore, the present study hypothesized that these differences in
genes and metabolites exhibited during the harvesting period of P. armandii seed kernels might be related to the
accumulation and transformation of sugars and lipids. This study may
provide a theoretical basis for determining the optimal harvesting
time of P. armandii seed kernels, changes
in the molecular mechanisms of nutrient accumulation, and quality
directed breeding.