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RNAseq reveals different transcriptomic responses to GA₃ in early and midseason varieties before ripening initiation in sweet cherry fruits.

ABSTRACT: Gibberellin (GA) negatively affects color evolution and other ripening-related processes in non-climacteric fruits. The bioactive GA, gibberellic acid (GA₃), is commonly applied at the light green-to-straw yellow transition to increase firmness and delay ripening in sweet cherry (Prunus avium L.), though causing different effects depending on the variety. Recently, we reported that GA₃ delayed the IAD parameter (a ripening index) in a mid-season variety, whereas GA₃ did not delay IAD but reduced it at ripeness in an early-season variety. To further explore this contrasting behavior between varieties, we analyzed the transcriptomic responses to GA₃ applied on two sweet cherry varieties with different maturity time phenotypes. At harvest, GA₃ produced fruits with less color in both varieties. Similar to our previous report, GA₃ delayed fruit color initiation and IAD only in the mid-season variety and reduced IAD at harvest only in the early-season variety. RNA-seq analysis of control- and GA₃-treated fruits revealed that ripening-related categories were overrepresented in the early-season variety, including 'photosynthesis' and 'auxin response'. GA₃ also changed the expression of carotenoid and abscisic acid (ABA) biosynthetic genes in this variety. In contrast, overrepresented categories in the mid-season variety were mainly related to metabolic processes. In this variety, some PP2Cs putative genes were positively regulated by GA₃, which are negative regulators of ABA responses, and MYB44-like genes (putative repressors of PP2Cs expression) were downregulated. These results show that GA₃ differentially modulates the transcriptome at the onset of ripening in a variety-dependent manner and suggest that GA₃ impairs ripening through the modification of ripening associated gene expression only in the early-season variety; whereas in the mid-season variety, control of the ripening timing may occur through the PP2C gene expression regulation. This work contributes to the understanding of the role of GA in non-climacteric fruit ripening.

SUBMITTER: Kuhn N

PROVIDER: S-EPMC8219793 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The sweet cherry is an important fruit species that is widespread globally. In addition to the well-known traditional and modern varieties, a myriad of landraces is present in Europe, as well as in southern Italy. This study aims to evaluate the population structure, genetic relationships, and cases of duplicate samples in a collection of 143 accessions using GBS-derived SNP markers. The genetic material under investigation includes modern commercial varieties, ancient European and American varieties, landraces, and individuals retrieved from small orchards. Some of the known varieties were genetically analyzed here for the first time. In addition, several genotypes were collected from the Basilicata region (southern Italy), an area largely unexplored for sweet cherry genetic resources. The relationships among genotypes were assessed using four different methods: allele frequency and ancestry estimation, principal component analysis, Neighbor-Joining tree, and identity-by-state estimation. The analyses returned quite congruent results and highlighted the presence of four main genetic groups, namely: (i) American varieties, (ii) the 'Germersdorfer-Ferrovia' cluster, (iii) the 'Burlat' group, and (iv) the group of Italian landraces. The main drivers of clustering were ancestry, geographical distribution, and some important traits such as self-compatibility. The sweet cherries from Basilicata, herewith examined for the first time, were mostly distributed within the group of Italian landraces, being particularly linked to the autochthonous varieties of the Campania region. However, some genotypes were outside this group, thus suggesting the introduction of genetic material from other Italian regions or from European countries. The considerable amount of American and European modern varieties analyzed are genetically very closely related, suggesting a reduced genetic basis. In addition, we highlighted the discriminating ability of SNP markers to distinguish between an original variety and its mutant. Overall, our results may be useful in defining conservation strategies for sweet cherry germplasm and developing future breeding programs to enlarge the genetic basis of commercial varieties.

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RNAseq reveals different transcriptomic responses to GA₃ in early and midseason varieties before ripening initiation in sweet cherry fruits.

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RNAseq reveals different transcriptomic responses to GA₃ in early and midseason varieties before ripening initiation in sweet cherry fruits.