Blueberries (Vaccinium species) belong to the Ericaceae family and are recognized for their antioxidant content and associated health-promoting properties. A key challenge in blueberry production is their asynchronous ripening with fruits on the same plant often maturing at different times. This leads to multiple harvests, increased production costs, and reduced overall fruit quality. Fruit ripening is a coordinated process wherein there is an increase in sugar concentration, decrease in acidity and accumulation of pigments such as anthocyanins. Blueberry fruit are classified as exhibiting atypical ripening behavior with an increase in respiration and ethylene during ripening. However, ethylene production is not autocatalytic and is under developmental regulation. Previous work from blueberry and other fruits have suggested a role of other hormones such as abscisic acid (ABA), auxin and jasmonates in fruit ripening. In this study, the cultivar Powderblue (Vaccinium ashei) was used to characterize the progression of ripening across multiple tissue types and developmental stages by examining the expression of key ripening-related genes. Fruits were harvested at five developmental stages including ripening. Ethylene was measured from these fruits to identify the stages that coincided with ripening initiation. For each stage, 9 tissue types were collected via dissection to obtain spatial resolution. RNA will be extracted from these tissues for qRT-PCR analyses to determine the expression of a focused-set of ripening related genes. For this study, a total of 37 genes were selected based on a previous RNA-Sequencing study that displayed a differential pattern in their transcript abundance during ripening. A subset of these genes is related to sugar, acid, anthocyanin, phenylpropanoid, photosynthesis, and cell wall metabolism. Further genes related to phytohormone metabolism related to ethylene, ABA, auxin, and jasmonates were included. Also, genes belonging to the NAC and MADS-box family of transcription factors were included. Based on the gene expression analysis, hormones including ABA, auxin and jasmonates will be quantified from a subset of these samples. This study will provide insights into the spatial context of molecular and hormone regulation. The knowledge from this study may help breeding programs aimed at developing cultivars exhibiting synchronous ripening, and the potential development of growth regulators to control ripening in the field.
