The role of auxin and sugar signaling in dominance inhibition of inflorescence growth by fruit load

Dominance inhibition of shoot growth by fruit load is a major factor that regulates shoot architecture and limits yield in agriculture and horticulture crops. In annual plants, the inhibition of inflorescence growth by fruit load occurs at a late stage of inflorescence development termed the end of flowering transition. Physiological studies show that this transition is mediated by production and export of auxin from developing fruits in close proximity to the inflorescence apex. In the meristem, cessation of inflorescence growth is controlled in part by the age dependent pathway, which regulates the timing of arrest. Here, results show that the end of flowering transition is a two-step process in which the first stage is characterized by a cessation of inflorescence growth, while immature fruit continue to develop. At this stage, dominance inhibition of inflorescence growth by fruit load correlates with a selective dampening of auxin transport in the apical region of the stem. Subsequently, an increase in auxin response in the vascular tissues of the apical stem where developing fruits are attached marks the second stage for the end of flowering transition. Similar to the vegetative and floral transition, the end of flowering transition correlates with a change in sugar signaling and metabolism in the inflorescence apex. Taken together, our results suggest that during the end of flowering transition, dominance inhibition of inflorescence shoot growth by fruit load is mediated by auxin and sugar signaling. One-sentence summaryDominance inhibition of inflorescence shoot growth by fruit load is involves auxin and sugar signaling during the end of flowering transition.