Carotenoids are essential for photosynthesis and photoprotection. Plants have evolved multifaceted regulatory mechanisms to control carotenoid biosynthesis. However, the regulatory mechanisms and the regulators conserved among plant species remain elusive. Phytoene synthase (PSY) catalyzes the highly regulated step of carotenogenesis and geranylgeranyl diphosphate synthase (GGPPS) acts as a hub to interact with GGPP-utilizing enzymes for the synthesis of specific downstream isoprenoids. Here, we report a function of Nudix hydrolase 23 (NUDX23), a Nudix domain-containing protein, in post-translational regulation of PSY and GGPPS for carotenoid biosynthesis. NUDX23 expresses highly in Arabidopsis (Arabidopsis thaliana) leaves. Overexpression of NUDX23 significantly increases PSY and GGPPS protein levels and carotenoid production, whereas knockout of NUDX23 dramatically reduces their abundances and carotenoid accumulation in Arabidopsis. NUDX23 regulates carotenoid biosynthesis via direct interactions with PSY and GGPPS in chloroplasts, which enhances PSY and GGPPS protein stability in a large PSY-GGPPS enzyme complex. NUDX23 was found to co-migrate with PSY and GGPPS proteins in a high molecular weight complex and to be required for the enzyme complex assembly. Our findings uncover a regulatory mechanism underlying carotenoid biosynthesis in plants and offer promising genetic tools for developing carotenoid-enriched food crops.

In agricultural production, rapid and accurate detection of peach blossom bloom plays a crucial role in yield prediction, and is the foundation for automatic thinning. The currently available manual operation-based detection and counting methods are extremely time-consuming and labor-intensive, and are prone to human error. In response to the above issues, this paper proposes a natural environment peach blossom detection model based on the YOLOv5 model. First, a cascaded network is used to add an output layer specifically for small target detection on the basis of the original three output layers. Second, a combined context extraction module (CAM) and feature refinement module (FSM) are added. Finally, the network clusters and statistically analyzes the range of multi-scale channel elements using the K-means++ algorithm, obtaining candidate box sizes that are suitable for the dataset. A novel bounding box regression loss function (SIoU) is used to fuse the directional information between the real box and the predicted box to improve detection accuracy. The experimental results show that, compared with the original YOLOv5s model, our model has correspondingly improved AP values for identifying three different peach blossom shapes, namely, bud, flower, and falling flower, by 7.8%, 10.1%, and 3.4%, respectively, while the final mAP value for peach blossom recognition increases by 7.1%. Good results are achieved in the detection of peach blossom flowering volume. The proposed model provides an effective method for obtaining more intuitive and accurate data sources during the process of peach yield prediction, and lays a theoretical foundation for the development of thinning robots.

Prunus species, also known as stone fruits, include several eye-catching fruits such as cherries, plums, apricots, peaches, nectarines, etc., which have significant economic value and are widely cultivated worldwide. Carotenoids are important secondary metabolites contributing to stone fruits' aesthetic appeal and nutritional value. Carotenoids contribute hues ranging from pastel yellow to rich orange in Prunus fruits. Carotenoids accumulate in Prunus tissues through the action of chromoplasts, particular structures that store and stabilize these pigments, giving rise to their vibrant colors. The diversity in carotenoid types and levels among Prunus species and cultivars leads to diverse tissue colors, reflecting their genetic diversity and evolutionary adaptations. The most important genes related to coloration are PSY, LCYB/E , and BCH1 , which are responsible for carotenoid biosynthesis, whereas CCDs and NCEDs are involved in the degradation of carotenoids. PSY leads to increased carotenoid accumulation, providing yellow and orange pigmentation. LCYB involved in β-carotene accumulation results in an orange color. LCYE can lead to lutein biosynthesis and contribute to yellow coloration. BCH1 contributes to yellow pigmentation. CCD4 plays an essential role in the flesh color of the fruit, leading to white flesh in Prunus fruits, especially peaches. NCED is involved in abscisic acid formation by degrading carotenoids. Despite the importance of carotenoids, the connection between carotenoid profiles and the diversity of Prunus fruits has received little attention in the past. This review outlines the present knowledge regarding the molecular diversity mechanisms of the carotenoid biosynthesis pathway in Prunus fruits.