Brassinosteroids: Biosynthesis, Signaling, and Hormonal Crosstalk as Related to Fruit Yield and Quality

Brassinosteroids (BRs) are plant growth regulators (PGRs) with pleiotropic effects on plant growth and development. They play a role in seed germination, vegetative and reproductive growth, photosynthetic efficiency, vascular differentiation, fruit yield, quality, and resilience to biotic and abiotic stresses. They engage in crosstalk with other hormones like auxin, gibberellins, ethylene and abscisic acid, influencing all plant growth and development aspects. Studies on the effect of BRs on the reproductive growth of fruit crops are accumulating, given the potential of this PGR as a management tool in agriculture. This review explores the multifaceted roles of BRs in fruit crop maturation. From their biosynthesis and signal transduction pathways to their influence on fruit production, development, and maturation, we focus on the effect of this plant hormone on different aspects of fruit yield and quality, including fruit set and firmness, sugar accumulation, and fruit development. We address BRs' interaction with different hormones at molecular and physiological levels in regulating these processes in climacteric and non-climacteric fruits. We also identify areas where knowledge is still lacking regarding hormonal crosstalk involving BRs in the regulation of developmental processes governing fruit quality and yield so knowledge generated can inform management decisions in fruit crop production.