Molecular Analysis of the Processes of Surface Brown Spot (SBS) Formation in Pear Fruit (Pyrus bretschneideri Rehd. cv. Dangshansuli) by De Novo Transcriptome Assembly

Abstract

Browning disorder, which usually occurs post-harvest in pears subjected to long-term storage, can cause browning of the pear flesh and/or core. In 2011, investigators in China found a novel type of brown spot (designated as surface brown spot, SBS) in pre-harvest ‘Dangshansuli’ pears (Pyrus bretschneideri Rehd.). SBS has a large impact on the exterior quality of the pears. Interestingly, the brown coloration was only found on the peel and not the flesh or the core. In this paper, de novo transcriptome analysis of the exocarp of pears with SBS using Illumina sequencing showed that SBS up-regulated the expression of genes related to oxidative phosphorylation, phenolic compound synthesis and polyphenoloxidase (PPO), and SBS was associated with inhibition of primary and secondary metabolism genes. Ca2+-sensor proteins might be involved in the signal transduction that occurs during the process of SBS formation, and this signaling is likely to be regulated by H2O2, abscisic acid (ABA) and gibberellic acid (GA3). Phytohormone and mineral element analyses confirmed that GA3, ABA, H2O2 and Ca2+ contribute to SBS formation. In addition to the seasonal characteristics, low levels of O2 and Ca2+ in the fruit are potential causes of the browning response due to exposure to oxidative stress, oxidative-reductive imbalance and the accumulation of reactive oxygen species (ROS), which affected the membrane integrity. Disruption of the membranes allows for PPO and phenolic compounds to come into contact, and the phenolic compounds are oxidized to form the browning pigments.

Genome-Wide Transcriptome and Expression Profile Analysis of Phalaenopsis during Explant Browning

“…To our knowledge, this is the first report to show that photosynthesis genes are associated with explant browning. Liu et al [ 18 ] also confirmed that photosynthesis changes during pear fruit browning. These metabolic processes will disrupt the energy metabolism providing a molecular context for the formation of ROS in browning tissue.…”

“…The energy-related and stress-related genes were also altered during apple fruit browning development. To investigate pear fruit surface brown (SBS), transcriptome analysis showed that up-regulated the expression of genes related to oxidative phosphorylation, phenolic compound synthesis and PPO [ 18 ]. These studies provide a genomics basis for botanists to understand the molecular mechanisms of enzymatic browning.…”

Proteomic analysis of peel browning of ‘Nanguo’ pears after low‐temperature storage

“…However, there is little knowledge available at the proteomic level, which would be valuable in understanding the molecular mechanisms of PB development in the ‘Nanguo’ pear. Transcriptomics analyses in pear fruit focusing on the peel brown spots have recently been reported . However, some discrepancies have been found between transcript content analysis and protein content analysis.…”

“…Transcriptomics analyses in pear fruit focusing on the peel brown spots have recently been reported. 5 However, some discrepancies have been found between transcript content analysis and protein content analysis. A more accurate method involves iTRAQ-based technology that can simultaneously label and accurately quantify proteins from multiple samples, 6,7 and it has been used to quantify and characterise changes in protein levels in a wide range of studies.…”

Genome-wide transcriptome profiling reveals novel insights into Luffa cylindrica browning

“…However, recent studies of transcriptomic profiles revealed that the expression of sequences associated with ethylene, abscisic acid and gibberellin metabolism were affected during browning of pear and apple [14,23]. In our transcriptomic analysis, an unigene annotated as IAA-amino acid hydrolase was up-regulated and four unigenes related with auxin efflux carrier were down-regulated in the YLB05 library (Table 3).…”