Regulatory Mechanisms of Parthenocarpic Fruit Set in Horticultural Crops

Fruits are an essential food component in the human diet. However, a growing number of prospective studies warn of the threat that climate change represents to the yield of these products. Climate breakdown may negatively affect fruit yields mainly through impairing flower pollination and fertilization, two critical processes known to be highly vulnerable to environmental changes, such as high/low temperatures, insufficient light intensity, and lack of winds or insect pollinators. To overcome these challenges, parthenocarpy represents the most economical solution to ensure yield stability via bypassing the pollination or fertilization processes. Moreover, parthenocarpic fruits have been reported to exhibit better texture, appearance, and shelf life, and be more amenable to food processing and many other agricultural applications. In the last few decades, significant breakthroughs have revealed the molecular mechanisms of parthenogenesis, where phytohormones such as auxin, gibberellin, and cytokine, interact to play pivotal roles in parthenocarpic fruit formation.
However, there are still many knowledge gaps to be filled. The key integrating molecular players are not yet well understood, and the complex regulatory mechanisms controlling hormone content, hormone responses, and the interplay between different hormone signaling pathways remain largely unresolved. To date, what is known about the regulatory network underlying parthenogenesis mainly focuses on the transcriptional level, while relatively few studies addressed the epigenetic regulation, non-encoding RNA, post-translational regulation, and small signaling peptides in parthenocarpic fruit formation. Even more strikingly, our knowledge of the molecular mechanisms controlling parthenogenesis has been mostly limited to the model plant tomato. Very few studies have been conducted on other horticultural crops, and only a few parthenocarpic varieties are currently used in agricultural production. Therefore, a comprehensive understanding of the mechanisms of parthenocarpic fruit formation is needed to further understand the regulatory factors on parthenogenesis and, hence, to define new targets for improving fruit yield.

This Research Topic aims to collect studies on the mechanisms of fruit formation, particularly those associated with parthenocarpy. We welcome papers in the research fields of (1) transcriptomic reprogramming and epigenetic regulation related to fruit set in different horticultural crops, (2) metabolomic and proteomic changes during parthenogenesis, and the interaction between genetic and environmental factors, (3) exploration of new regulatory factors, small peptide hormones, and chemical compounds that promote the formation of parthenocarpic fruit, (4) breeding strategies and gene mapping studies aiming to improve parthenocarpy, and (5) the impact of parthenocarpy on industrial processing. We accept any article types, including original research articles, hypotheses and theories, methods, reviews, mini reviews, perspectives, etc.

We encourage authors to submit articles about flower-fruit transition and parthenocarpic fruit development in horticulture crops and Arabidopsis. We welcome all article types on the following subthemes but are not limited to:

• Identifying and functional analysis of key genes controlling fruit set and parthenocarpic fruit formation

• Mechanisms of flower-fruit transition, seedless fruit formation

• Screening and developing important molecular markers of parthenocarpic fruit.

• Application of genetic mapping and gene editing technology of parthenocarpic fruit

• Epigenetic regulation of flower-fruit transition and parthenocarpic fruit development.