Abstract
BackgroundZucchini fruit set can be limited due to unfavourable environmental conditions in off-seasons crops that caused ineffective pollination/fertilization. Parthenocarpy, the natural or artificial fruit development without fertilization, has been recognized as an important trait to avoid this problem, and is related to auxin signalling. Nevertheless, differences found in transcriptome analysis during early fruit development of zucchini suggest that other complementary pathways could regulate fruit formation in parthenocarpic cultivars of this species. The development of next-generation sequencing technologies (NGS) as RNA-sequencing (RNA-seq) opens a new horizon for mapping and quantifying transcriptome to understand the molecular basis of pathways that could regulate parthenocarpy in this species. The aim of the current study was to analyze fruit transcriptome of two cultivars of zucchini, a non-parthenocarpic cultivar and a parthenocarpic cultivar, in an attempt to identify key genes involved in parthenocarpy.ResultsRNA-seq analysis of six libraries (unpollinated, pollinated and auxin treated fruit in a non-parthenocarpic and parthenocarpic cultivar) was performed mapping to a new version of C. pepo transcriptome, with a mean of 92% success rate of mapping. In the non-parthenocarpic cultivar, 6479 and 2186 genes were differentially expressed (DEGs) in pollinated fruit and auxin treated fruit, respectively. In the parthenocarpic cultivar, 10,497 in pollinated fruit and 5718 in auxin treated fruit. A comparison between transcriptome of the unpollinated fruit for each cultivar has been performed determining that 6120 genes were differentially expressed. Annotation analysis of these DEGs revealed that cell cycle, regulation of transcription, carbohydrate metabolism and coordination between auxin, ethylene and gibberellin were enriched biological processes during pollinated and parthenocarpic fruit set.ConclusionThis analysis revealed the important role of hormones during fruit set, establishing the activating role of auxins and gibberellins against the inhibitory role of ethylene and different candidate genes that could be useful as markers for parthenocarpic selection in the current breeding programs of zucchini.
Highlights
Zucchini fruit set can be limited due to unfavourable environmental conditions in off-seasons crops that caused ineffective pollination/fertilization
Parthenocarpy, fruit development in the absence of pollination/fertilization, has been recognized as an important trait to avoid this problem in different fruit crops [3], considering than each species shows specific responses following pollination/ fertilization, In Cucurbita, the most practical mean of Pomares-Viciana et al BMC Plant Biology (2019) 19:61 increasing fruit set of zucchini when pollination/ fertilization is inadequate would be the use of cultivars with vegetative parthenocarpy, innate ability to set parthenocarpic fruit [4], but this kind of parthenocarpy is limited to a few cultivars in C. pepo
For several cultivars of zucchini, we provided previously an exhaustive description of the specific changes in fruit set observed after successful pollination or parthenocarpy, when compared with non-pollination [5]
Summary
Zucchini fruit set can be limited due to unfavourable environmental conditions in off-seasons crops that caused ineffective pollination/fertilization. Fertilization occurs in the ovule, and requires pollen tubes growth in the stylar tissue and fusion with the egg cell [1]. Parthenocarpy, fruit development in the absence of pollination/fertilization, has been recognized as an important trait to avoid this problem in different fruit crops [3], considering than each species shows specific responses following pollination/ fertilization, In Cucurbita, the most practical mean of Pomares-Viciana et al BMC Plant Biology (2019) 19:61 increasing fruit set of zucchini when pollination/ fertilization is inadequate would be the use of cultivars with vegetative parthenocarpy, innate ability to set parthenocarpic fruit [4], but this kind of parthenocarpy is limited to a few cultivars in C. pepo. For several cultivars of zucchini, we provided previously an exhaustive description of the specific changes in fruit set observed after successful pollination or parthenocarpy, when compared with non-pollination [5]
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