The curvature of cucumber fruits is associated with spatial variation in auxin accumulation and expression of a YUCCA biosynthesis gene

Abstract

Fruit curving lowers the commercial value of cucumber and leads to significant economic losses. The mechanism driving the abnormal curving of cucumber is largely unknown. Through our previous work, we discovered that 2 days post-anthesis (DPA) was the key time point at which various phenotypic and genotypic characteristics of cucumber fruits are determined. Here, we analyzed the transcriptome of the concave (C1) and convex (C2) sides of curved fruits at 2 DPA by Gene Ontology (GO) enrichment and functional pathway enrichment analyses and identified auxin as a putative factor influencing fruit curvature. Changes in the curve angle in the fruits and exogenous auxin treatment analyses showed that asymmetric auxin distribution induces fruit curving. Identification of differentially expressed genes (DEGs) related to auxin and qPCR validation showed that CsYUC10b had the most significant differential expression when both sides of the curved fruits were compared. Gene functional analysis showed that the transcript levels of CsYUC10b and the auxin concentration were even on both sides of the fruit in CsYUC10b-overexpressing plants, which in turn contributed to an equal rate of growth of both sides of cucumber fruits and resulted in a straight shape of the fruits. Thus, we conclude that CsYUC10b promotes the formation of straight cucumber fruits, with possible applications in the production and breeding of cucumber.

Phenotypic Characteristics and Transcriptome of Cucumber Male Flower Development Under Heat Stress

“…Furthermore, RNA-seq has also been widely applied to investigate the differently expressed genes in cucumber. For instance, transcriptome technique was applied in cucumber to study the floral sex determination (Guo et al, 2010;Wu et al, 2010), fruit curving (Li et al, 2020), fruit spine (Xie et al, 2018), salt stress (Jiang et al, 2020), and disease resistant (Yang et al, 2020). He et al (2020) reported that cucumber respond to hightemperature stress by full transcriptomic analysis and integrated the potential ceRNA function of lncRNAs/circRNAs for the first time in response to high-temperature stress.…”

NS encodes an auxin transporter that regulates the ‘numerous spines’ trait in cucumber (Cucumis sativus) fruit

“…Moreover, auxin can also promote adventitious root formation (Qi et al., 2019); CsPIN5 plays an important role in inducing root hydrotropism (Morohashi et al., 2017). The curvature of cucumber fruits is associated with spatial variation in auxin accumulation (Li et al., 2020). However, whether auxin plays a role in the regulation of cucumber fruit spine development is not clear.…”

Morphological and Genetic Diversity of Cucumber (Cucumis sativus L.) Fruit Development

“…Subsequently, critical components influencing fruit size and shape include timing and level of expression of genes involved in cell division and cell cycle regulation during ovary development and early fruit set [ 3 , 12 , 13 , 15 , 16 , 148 ]. Not surprisingly, many of the genes affecting cell division, both pre- and post-pollination, have been shown to be associated with modified expression of genes involved in hormone biosynthesis, transport, degradation or inactivation, which in turn, influence extent and orientation of cell division (e.g., [ 15 , 16 , 21 , 23 , 79 , 150 ]). Genes influencing cell expansion via sugar transport and phloem unloading also can contribute to variation in size, shape, and internal fruit structure [ 18 , 19 , 146 ].…”

“…Fruit curvature is a negative trait for cucumbers, lowering its marketability. Analysis of the convex and concave regions of cucumber fruit during the phase of active cell division and early expansion, 2–6 days post anthesis, showed asymmetric distribution of auxin and differential expression of auxin-related genes, including the auxin ( YUCCA ) biosynthesis gene, CsYUC10b [ 79 ]. Treatment with auxin or overexpression of CsYUC10b reduced the curvature angle of developing fruits, providing another example of the important role auxin plays in multiple aspects of cucumber fruit growth and development.…”