Relationship between H2O2 in Polyamine Metabolism and Lignin in the Exocarp of a Russet Mutant of ‘Dangshansuli’ Pear (Pyrus bretschneideri Rehd.)

Abstract

The fruit of the 'Dangshansuli' pear has a greenish yellow skin, whereas its mutant, the 'Xiusu' pear, has a russet skin, which represents a genetic variation. It has been demonstrated that the formation of russet fruit in the 'Xiusu' pear is related to lignin accumulation in skin exocarp cells. In this study, we localized hydrogen peroxide (H 2 O 2 ) to the cell wall using transmission electron microscopy (TEM) and quantified the concentrations of H 2 O 2 and polyamines. In addition, the expression levels of genes involved in polyamine biosynthesis were measured in the exocarps of samples of young fruits of 'Dangshansuli', 'Xiusu', 'Xiusu' treated with methylglyoxal bis(guanylhydrazone), and 'Xiusu' treated with ethephon. The results obtained could explain the mechanism by which H 2 O 2 participates in polyamine metabolism in the lignification of exocarp cells in the russet fruit mutant. The TEM results showed that free H 2 O 2 is present near the cell wall, where lignin is primarily synthesized, and the H 2 O 2 concentration was highly positively correlated with the lignin concentration. Although H 2 O 2 related to lignification showed no significant correlation with the putrescine or spermine concentration, it was highly positively correlated with the spermidine (Spd) concentration. Additionally, the Spd concentration was significantly positively correlated with altered expression of the polyamine oxidase gene (PbPAO). Taken together, these results have demonstrated that H 2 O 2 involved in lignification originates from the oxidation of Spd by the enzyme PAO, with high expression of the PbPAO gene, which suggests that H 2 O 2 from polyamine metabolism affects lignification in the exocarp of the russet mutant pear.

Lignin and Quercetin Synthesis Underlies Berry Russeting in ‘Sunshine Muscat’ Grape

“…Studies on pears and apples have highlighted that lignin synthesis genes, such as COMT and C4H, have increased expression, underlying the lignin accumulation that leads to russet formation [5,27]. Studies on 'Dangshansu Pear' mutant varieties have shown that increased expression of CCoAOMT leads to an increase in the lignin content of the outer peel, which results in russet formation [28]. Similar results were observed in this study.…”

Study on russet-related enzymatic activity and gene expression in ‘Shine Muscat’ grape treated with GA3 and CPPU

“…It also increases parthenocarpic fruit set in apple (Watanabe et al 2008) and extends the shelf-life of grape and blueberry (Nesmith 2002). Limited studies have been conducted to address the russet problem in 'Shine Muscat' grapes by applying different concentrations of GA 3 and CPPU to gain insight into the molecular mechanism underlying fruit russet (Wang, Li, et al 2014;Heng et al 2016;Liang et al 2016;Wang et al 2017). The present study is the first one to simultaneously explore the physiological and molecular mechanisms associated with the russet problem in grape berries.…”

PpMYB36 Encodes a MYB-Type Transcription Factor That Is Involved in Russet Skin Coloration in Pear (Pyrus pyrifolia)

“…Russet skin is a vital trait affecting both fruit quality and stress tolerance in pear. Although several studies on russet pear have enabled a better comprehension of the mechanical causes responsible for this phenomenon ( Heng et al, 2016 ; Shi et al, 2019b ), the genetic and molecular mechanisms underpinning russet skin coloration have not been thoroughly investigated.…”

“…Previous studies have shown that lignin biosynthesis can regulate russet skin formation in the russet skin mutant DSS of pear ( Heng et al, 2016 ). Here, we observed considerably higher lignin contents in russet skin fruits than in non-russet skin fruits ( Figure 1C ), yet chlorophyll contents were not significantly different between the two fruit types ( Figure 1B ).…”