Transcriptome Analysis and Ultrastructure Observation Reveal that Hawthorn Fruit Softening Is due to Cellulose/Hemicellulose Degradation

Abstract

Softening, a common phenomenon in many fruits, is a well coordinated and genetically determined process. However, the process of flesh softening during ripening has rarely been described in hawthorn. In this study, we found that ‘Ruanrou Shanlihong 3 Hao’ fruits became softer during ripening, whereas ‘Qiu JinXing’ fruits remained hard. At late developmental stages, the firmness of ‘Ruanrou Shanlihong 3 Hao’ fruits rapidly declined, and that of ‘Qiu JinXing’ fruits remained essentially unchanged. According to transmission electron microscopy, the middle lamella of ‘Qiu JinXing’ and ‘Ruanrou Shanlihong 3 Hao’ fruit flesh was largely degraded as the fruits matured. Microfilaments in ‘Qiu JinXing’ flesh were arranged close together and were deep in color, whereas those in ‘Ruanrou Shanlihong 3 Hao’ fruit flesh were arranged loosely, partially degraded and light in color. RNA-Seq analysis yielded approximately 46.72 Gb of clean data and 72,837 unigenes. Galactose metabolism and pentose and glucuronate interconversions are involved in cell wall metabolism, play an important role in hawthorn texture. We identified 85 unigenes related to the cell wall between hard- and soft-fleshed hawthorn fruits. Based on data analysis and real-time PCR, we suggest that β-GAL and PE4 have important functions in early fruit softening. The genes Ffase, Gns,α-GAL, PE63, XTH, and CWP, which are involved in cell wall degradation, are responsible for the different textures of hawthorn fruits. Thus, we hypothesize that the different textures of ‘Qiu JinXing’ and ‘Ruanrou Shanlihong 3 Hao’ fruits at maturity mainly result from cellulose/hemicelluloses degradation rather than from lamella degradation. Overall, we propose that different types of hydrolytic enzymes in cells interact to degrade the cell wall, resulting in ultramicroscopic Structure changes in the cell wall and, consequently, fruit softening. These results provide fundamental insight regarding the mechanisms by which hawthorn fruits acquire different textures and also lay a solid foundation for further research.

Transcriptome analysis reveals delaying of the ripening and cell‐wall degradation of kiwifruit by hydrogen sulfide

“…Due to ripening and senescence after harvest, kiwifruit quality will be seriously affected, and the storage period will be shortened because of membrane deterioration, cell‐wall degradation, cell‐structure modification, and cell death . Cell‐wall degradation is associated with cell‐wall hydrolases, including pectinesterase (PME), polygalacturonase (PG), β ‐gal, α ‐arabinofuranosidase ( α ‐L‐af), xyloglucan endotransglycosylase / hydrolase (XTH), and cellulase . Pectinesterase catalyzes the demethylesterification of cell‐wall polygalacturonans, which promotes the hydrolysis of polygalacturonic acid by PG .…”

“…6 Cell-wall degradation is associated with cell-wall hydrolases, including pectinesterase (PME), 7 polygalacturonase (PG), 8,9 ⊎-gal, 10 ⊍-arabinofuranosidase (⊍-L-af), 11,12 xyloglucan endotransglycosylase / hydrolase (XTH), 13,14 and cellulase. 15 Pectinesterase catalyzes the demethylesterification of cell-wall polygalacturonans, 16 which promotes the hydrolysis of polygalacturonic acid by PG. 17 ⊎-Gal is hydrolyzed to pectin and hemicellulose, as a pectin-debranching enzyme.…”

Transcriptome analysis of table grapes (Vitis vinifera L.) identified a gene network module associated with berry firmness

“…However, VvXTH and VvEXP were significantly upregulated in ‘Muscat Hamburg’ compared with ‘Red Globe’. In addition, the transcript encoding Vvβ-GAL showed a similar gene expression pattern as that of VvEXP , suggesting that Vvβ-GAL may be related to berry firmness, as these genes are involved in fruit softening [ 37 – 39 ].…”

An RNA Sequencing Transcriptome Analysis and Development of EST-SSR Markers in Chinese Hawthorn through Illumina Sequencing

“…In the previous research, an RNA-Seq experiment was conducted using Illumina HiSeq 2500 by Xu and Dong [43]. The accession number was PRJNA339788.…”

“…Yang et al [42] used RNA-seq analysis identified numerous candidate genes involved in the hawthorn (C. pinnatifida) biosynthesis of polyphenolic compounds. Xu et al [43] used RNA-Seq analysis to study soft and hard flesh textures in hawthorn (C. pinnatifida) fruits. All these research studies aided the studies on the development of expressed sequence tag SSRs (EST-SSRs), which are located in the flanking coding region and identified from transcribed RNA sequence, while the genomic SSRs (g-SSRs) are identified from random genomic sequences [44].…”