Differential Expression of Genes Related to Fruit Development and Capsaicinoids Synthesis in Habanero Pepper Plants Grown in Contrasting Soil Types

Habanero pepper (Capsicum chinense Jacq.) is a crop of economic relevance in the Peninsula of Yucatan. Its fruits have a high level of capsaicinoids compared to peppers grown in other regions of the world, which gives them industrial importance. Soil is an important factor that affects pepper development, nutritional quality, and capsaicinoid content. However, the effect of soil type on fruit development and capsaicinoid metabolism has been little understood. This work aimed to compare the effect of soils with contrasting characteristics, black soil (BS) and red soil (RS), on the expression of genes related to the development of fruits, and capsaicinoid synthesis using a transcriptomic analysis of the habanero pepper fruits. Plants growing in RS had bigger fruits and higher expression of genes related to floral development, fruit abscission, and softening which suggests that RS stimulates fruit development from early stages until maturation stages. Fruits from plants growing in BS had enrichment in metabolic pathways related to growth, sugars, and photosynthesis. Besides, these fruits had higher capsaicinoid accumulation at 25 days post-anthesis, and higher expression of genes related to the branched-chain amino acids metabolism (ketol-acid reductisomerase KARI), pentose phosphate pathway and production of NADPH (glucose-6-phosphate-1-dehydrogenase G6PDH), and proteasome and vesicular traffic in cells (26S proteasome regulatory subunit T4 RPT4), which suggest that BS is better in the early stimulation of pathways related to the nutritional quality and capsaicinoid metabolism in the fruits.