No abstract

Kiwifruit are climacteric fruit, so they must be harvested before they are fully ripe, 26 allowing for the extension of their shelf-life via cold storage. Therefore, an adequate 27 knowledge about how ethylene-induced fruit senescence is required to avoid significant 28 economic losses. The main goal of the present study was to investigate the kiwifruit 29 ripening process at the physiological and molecular levels by RNA-seq after 1-MCP 30 (ethylene inhibitor) and Ethrel® (ethylene stimulator) treatments. The results showed that 31 Ethrel® (ethephon) treatment induced more accelerated fruit ripening, leading to rapid 32 fruit senescence, meanwhile 1-MCP (1-Methylcyclopropene) caused a slowing flesh 33 softening, and thus a longer shelf-life period. The RNA-seq was carried out on the fruit 34 after 4 and 13 days, considering day 4 as the most determinant in terms of differentially 35 Manuscript Click here to access/download;Manuscript;Salazar et al. TGG_corrected version.docx Click here to view linked References expressed genes (DEGs). The sequencing achieved 70.7 % alignment with the 36 'Hongyang' genome, obtaining 18,036 DEGs. The protein-protein interaction (PPI) 37 network shows the interaction between different pathways in two main clusters: (1) 38 pentose and glucoronate interconversions, citrate cycle, glycolysis and gluconeogenesis 39 or starch and sucrose metabolism and (2) porphyrin and chlorophyll metabolism. The first 40 cluster is mainly interconnected by G6PD1 (pentose pathway); E1 ALPHA and ACLB-2 41 (citrate cycle); Achn209711 (pentose and glucoronate); LOS2 (glycolysis); HKL1 and 42 HXK1 (glycolysisstarch and sucrose); and PHS2 (starch and sucrose). In the second 43 cluster GUN5 through PORA is interacting with CRD1 and NYC1 which were 44 overexpressed by 1-MCP in the porphyrin and chlorophyll metabolism. In addition, genes 45 linked to PSBY and PSBP photosynthesis-linked proteins in photosystem 2 were 46 overexpressed by 1-MCP which is undoubtedly related to chlorophyll degradation and 47 fruit senescence. These results suggest that in kiwifruit the main pathways that are 48 regulated by ethylene-induced senescence comprise sugar catabolism and chlorophyll 49 degradation.

Kiwifruit (Actinidia deliciosa [A. Chev.], C.V. Liang & A. R. Ferguson, 1984) is a perennial plant, with morphologically hermaphroditic and functionally dioecious flowers. Fruits of this species are berries of great commercial and nutritional importance. Nevertheless, few studies have analyzed the molecular mechanisms involved in sexual differentiation in this species. To determine these mechanisms, we performed RNA-seq in floral tissue at stage 60 on the BBCH scale in cultivar ‘Hayward’ (H, female) and a seedling from ‘Green Light’ × ‘Tomuri’ (G × T, male). From these analyses, we obtained expression profiles of 24,888 (H) and 27,027 (G × T) genes, of which 6413 showed differential transcript abundance. Genetic ontology (GO) and KEGG analysis revealed activation of pathways associated with the translation of hormonal signals, plant-pathogen interaction, metabolism of hormones, sugars, and nucleotides. The analysis of the protein-protein interaction network showed that the genes ERL1, AG, AGL8, LFY, WUS, AP2, WRKY, and CO, are crucial elements in the regulation of the hormonal response for the formation and development of anatomical reproductive structures and gametophytes. On the other hand, genes encoding four Putative S-adenosyl-L-methionine-dependent methyltransferases (Achn201401, Achn281971, Achn047771 and Achn231981) were identified, which were up-regulated mainly in the male flowers. Moreover, the expression profiles of 15 selected genes through RT-qPCR were consistent with the results of RNA-seq. Finally, this work provides gene expression-based interactions between transcription factors and effector genes from hormonal signaling pathways, development of floral organs, biological and metabolic processes or even epigenetic mechanisms which could be involved in the kiwi sex-determination. Thus, in order to decode the nature of these interactions, it could be helpful to propose new models of flower development and sex determination in the Actinidia genus.