Sodium dichloroisocyanurate delays ripening and senescence of banana fruit during storage

F-box protein EBF1 and transcription factor ABI5-like regulate banana fruit chilling-induced ripening disorder

Cold stress adversely affects plant production, both qualitatively and quantitatively. Banana (Musa acuminata) is sensitive to cold stress and suffers chilling injury (CI) when stored under 11°C, causing abnormal fruit softening. However, the mechanism underlying the abnormal fruit softening due to CI remains obscure. This study uncovered the coordinated transcriptional mechanism of ethylene F-box (EBF1) protein and abscisic acid-insensitive 5 (ABI5)-like protein in regulating chilling-induced softening disorders of Fenjiao banana. Cold stress severely inhibited the transcript and protein levels of EBF1, ABI5-like, and fruit softening-related genes. The ABI5-like protein bound to the promoters of key starch and cell wall degradation-related genes such as β-amylase 8 (BAM8), pectate lyase 8 (PL8), and β-D-xylosidase23-like (XYL23-like) and activated their activities. EBF1 physically interacted with ABI5-like and enhanced the transcriptional activity of the key starch and cell wall degradation-related genes but did not ubiquitinate or degrade ABI5-like protein. This promoted fruit ripening and ameliorated fruit CI in a manner similar to the effect of exogenous abscisic acid treatment. The ectopic and transient overexpression of EBF1 and ABI5-like genes in tomato (Solanum lycopersicum) and Fenjiao banana accelerated fruit ripening and softening by promoting ethylene production, starch and cell wall degradation, and decreasing fruit firmness. EBF1 interacted with EIL4 but did not ubiquitinate or degrade EIL4, which is inconsistent with the typical role of EBF1/2 in Arabidopsis (Arabidopsis thaliana). These results collectively highlight that the interaction of EBF1 and ABI5-like controls starch and cell wall metabolism in banana, which is strongly inhibited by chilling stress, leading to fruit softening and ripening disorder.

Transcriptome profiling helps to elucidate the mechanisms of ripening and epidermal senescence in passion fruit (Passiflora edulia Sims)

Passion fruit (Passiflora edulia Sims), an important tropical and subtropical species, is classified as a respiration climacteric fruit, and its quality deteriorates rapidly after harvest. To elucidate the mechanisms involved in ripening and rapid fruit senescence, phytochemical characteristic analysis and RNA sequencing were performed in purple passion fruit with different treatments, that is, 1-methylcyclopropene (1-MCP) and preservative film (PF). Comprehensive functional annotation and KEGG enrichment analysis showed that starch and sucrose metabolism, plant hormone signal transduction, phenylpropanoid biosynthesis, flavonoid biosynthesis, and carotenoid biosynthesis were involved in fruit ripening. Treatment with PF and 1-MCP significantly affected the transcription levels of passion fruit during postharvest storage. A large number of differentially expressed unigenes (DEGs) were identified as significantly enriched in starch and sucrose metabolism, plant hormone signal transduction and phenylpropanoid biosynthesis at the postharvest stage. The PF and 1-MCP treatments increased superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) gene expression levels and enzyme activities, accelerated lignin accumulation, and decreased β-galactosidase (β-Gal), polygalacturonase (PG) and cellulose activities and gene expression levels to delay cell wall degradation during fruit senescence. The RNA sequencing data for cell wall metabolism and hormone signal transduction pathway-related unigenes were verified by RT-qPCR. The results of this study indicate that the cell wall metabolism and hormone signaling pathways are closely related to passion fruit ripening. PF and 1-MCP treatment might inhibit ethylene signaling and regulate cell wall metabolism pathways to inhibit cell wall degradation. Our results demonstrate the involvement of ripening- and senescence-related networks in passion fruit ripening and may establish a foundation for future research investigating the effects of PF and 1-MCP treatment on fruit ripening.

GC-MS Based Metabolite Profiling to Monitor Ripening-Specific Metabolites in Pineapple (Ananas comosus)

Pineapple is one of the most cultivated tropical, non-climacteric fruits in the world due to its high market value and production volume. Since non-climacteric fruits do not ripen after harvest, the ripening stage at the time of harvest is an important factor that determines sensory quality and shelf life. The objective of this research was to investigate metabolite changes in the pineapple ripening process by metabolite profiling approach. Pineapple (Queen variety) samples from Indonesia were subjected to GC-MS analysis. A total of 56, 47, and 54 metabolites were annotated from the crown, flesh, and peel parts, respectively. From the principal component analysis (PCA) plot, separation of samples based on ripening stages from C0-C2 (early ripening stages) and C3-C4 (late ripening stages) was observed for flesh and peel parts, whereas no clear separation was seen for the crown part. Furthermore, orthogonal projection to latent structures (OPLS) analysis suggested metabolites that were associated with the ripening stages in flesh and peel parts of pineapple. This study indicated potentially important metabolites that are correlated to the ripening of pineapple that would provide a basis for further study on pineapple ripening process.