Transcriptome and Metabolomic Analysis to Reveal the Browning Spot Formation of ‘Huangguan’ Pear

Abstract

Background: Browning spot (BS) disorders seriously affect the appearance quality of ‘Huangguan’ pear and cause economic losses. Many studies on BS have mainly focused on physiological and biochemical aspects, and the molecular mechanism is unclear.Result: In the present study, the structural characteristics of ‘Huangguan’ pear with BS were observed with SEM, the water loss and brown spot were evaluated, and transcriptome and metabonomics analyses were conducted to reveal the molecular mechanism of ‘Huangguan’ pear skin browning disorder. The results showed that the occurrence of BS was accompanied by a decrease in the wax layer and an increase in lignified cells. It appears that genes related to wax biosynthesis were down-regulated in BS, resulting in the decrease of wax layer in BS. Genes related to lignin were up-regulated at transcriptional level, resulting in upregulation of metabolites related to phenylpropanoid biosynthesis. Expression of calcium-related genes were upregulated in BS. The cold-induced genes CS120, LTI65 and RCI2B may be the key genes that induce BS. In addition, the results demonstrated that exogenous NaH2PO4·2H2O and ABA treatment could inhibit the incidence of BS during harvest and storage time by increasing the expression of wax-related genes and calcium-related genes and increasing plant resistance, whereas GA3may accelerate the incidence and index of BS in transcriptomics.Conclusions: The results of this study would provide a basis for the molecular mechanism of BS formation and clarify the effects of different treatments on the incidence and molecular regulation of BS.

Identification of bZIP transcription factors and their responses to brown spot in pear

“…In studies of Arabidopsis thaliana, transcription of AtbZIP44 was responsive to temperature, and under ABA, salt and osmotic stress, transcription of AtbZIP53 was upregulated in seeds, and transcription of AtbZIP2 was downregulated in roots (Kang et al, 2002;Weltmeier et al, 2009). BS is reported to be associated with light irradiation, sudden drops in temperature, calcium deficiency, and various physiological, developmental and hormonal responses (Li et al, 2008;Wang et al, 2011;Wang et al, 2021). These results provide evidence of the potential involvement of bZIP genes in the formation of BS on the surface of 'Huangguan' pear.…”

“…In this study, a bioinformatics method was used for genome-wide identification of the bZIP gene family in white pear, and the gene structure, physicochemical properties, conserved motifs, phylogenetic relationships, chromosomal locations, collinearity and cis-acting elements of bZIP family members were analyzed. In our previous study, we found that gibberellin A 3 (GA 3 ) has a promoting effect on brown spot (BS) (Wang et al, 2021). In the present study, the expression levels of bZIP genes in exocarp of 'Huangguan' pear were evaluated in normal fruit, fruit with BS and fruit treated with GA 3 .…”

“…The results showed that the fruit size increased significantly after GA 3 treatment (Figure 4A). In our previous study, we found that the GA signaling pathway may be the key pathway regulating the occurrence of BS (Wang et al, 2021). Based on the transcriptome analysis, 8 PbbZIP genes were identified, most of which were significantly upregulated in pears with BS compared with healthy pears.…”

“…An RNA-seq dataset (PRJNA682706) of pear subjected to several different treatments, including NaH 2 PO 4 •2H 2 O (0.2%, Sigma 04269), ABA (100 μM, Sigma A1049), and GA 3 (300 mg/L, Sigma G8040), as well as normal fruits and fruits with BS disease, was obtained from our previous work (Wang et al, 2021). Each had three biological replicates.…”

Transcriptomic Analysis of Hardened ‘Suli’ Pear (Pyrus bretschneideri Rehd) for Identification of Key Genes for Lignin Biosynthesis and Accumulation

“…In pear fruit, stone cell growth relies in the biosynthesis of two types of lignin, namely, guaiacyl lignin (G-lignin) and syringyl lignin (S-lignin) [14,15]. For different pear varieties and developmental stages, structural genes were identified as hub genes involved in the lignin pathway [16][17][18][19][20], Table S1. Pears are rich in various lignin biosynthesis genes since the expansion of lignin synthesis gene family contributes to the large accumulation of lignin [21].…”