A high soluble-fibre allele in wheat encodes a defective cell wall peroxidase responsible for dimerization of ferulate moieties on arabinoxylan
A high soluble-fibre allele in wheat encodes a defective cell wall peroxidase responsible for dimerization of ferulate moieties on arabinoxylan
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DOI：
10.1101/2023.03.08.531735
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发表时间：
2023-03
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通讯作者：
R. Mitchell;Mária Oszvald;T. Pellny;J. Freeman;K. Halsey;C. Sparks;A. Huttly;S. Specel;M. Leverington-Waite;S. Griffiths;P. Shewry;A. Lovegrove
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作者：
R. Mitchell;Mária Oszvald;T. Pellny;J. Freeman;K. Halsey;C. Sparks;A. Huttly;S. Specel;M. Leverington-Waite;S. Griffiths;P. Shewry;A. Lovegrove
增加膳食纤维（DF）摄入量是改善健康的一个重要目标，一个有吸引力的策略是增加主食的纤维含量，特别是白色面包，它是许多国家的主食。小麦白色面粉中的膳食纤维主要来源于胚乳细胞壁多糖阿拉伯木聚糖（AX），其水提取形式（WE-AX）占可溶性膳食纤维（SDF）的大部分，据信其赋予特别的健康益处。我们之前在小麦双亲群体中确定了1B和6 B染色体上可溶性膳食纤维（SDF）的QTL。在这里，我们表明，6 B高SDF等位基因编码的过氧化物酶蛋白（PER 1-V）与一个单一的错义相比，更常见的低SDF形式（PER 1）。具有天然PER 1-v等位基因和在PER 1中具有诱导敲除突变的小麦品系表现出与水可提取的WE-AX相关的阿魏酸二聚化减少的相似特征。降低的阿魏酸二聚化与WE-AX链的交联降低和AX的溶解度增加相关。在小麦胚乳中由天然启动子驱动的瞬时表达的PER1_RFP融合显示定位于细胞壁，而PER 1-v_RFP没有;因此，我们提出PER 1-v由于错误定位而缺乏在体内二聚化AX阿魏酸的能力。PER 1是第一个被报道负责AX上阿魏酸氧化偶联的过氧化物酶，这是所有草细胞壁中的关键过程。了解它的作用和变体对AX特性的影响，为控制人类饮食中小麦DF的特性提供了一条途径。
Increasing dietary fibre (DF) intake is an important target to improve health and an attractive strategy for this is to increase the fibre content of staple foods, particularly white bread which is the staple food in many countries. DF in wheat white flour is derived principally from the endosperm cell wall polysaccharide arabinoxylan (AX) and the water-extractable form of this (WE-AX) accounts for the majority of soluble dietary fibre (SDF), which is believed to confer particular health benefits. We previously identified QTLs for soluble dietary fibre (SDF) on 1B and 6B chromosomes in wheat in biparental populations. Here we show that the 6B high SDF allele encodes a peroxidase protein (PER1-v) with a single missense compared to the more common low SDF form (PER1). Wheat lines with the natural PER1-v allele and with an induced knock-out mutation in PER1 showed similar characteristics of reduced dimerization of ferulate associated with water-extractable WE-AX. Decreased ferulate dimerization is associated with decreased cross-linking of the WE-AX chains and increased solubility of AX. Transiently expressed PER1_RFP fusion driven by native promoter in wheat endosperm was shown to localise to cell walls whereas PER1-v_RFP did not; we therefore propose that PER1-v lacks capacity to dimerise AX ferulate in vivo due to mis-localisation. PER1 is the first peroxidase reported to be responsible for oxidative coupling of ferulate on AX, a key process in all grass cell walls. Understanding its role and the effect of variants on AX properties offers a route to control the properties of wheat DF in the human diet.