豌豆不同耐铝品种根尖细胞壁果胶及其甲基酯化度的差异

【目的】研究豌豆不同品种耐铝性和根尖根段耐铝性与果胶及其甲基酯化间的关系,为进一步揭示植物耐铝机理以及耐铝性状的遗传改良提供依据。【方法】以豌豆品种Hyogo和Alaska为试验材料,采用Hoagland培养方式,测定了不同品种不同根段果胶含量、 果胶甲基酯化度和果胶甲酯酶活性,研究了其差异及原因。【结果】在15和30 μmol/L铝浓度胁迫条件下,豌豆品种Alaska根相对伸长率均显著高于品种Hyogo,同时有根尖0~5 mm和5~10 mm段有更少的胼胝质生成和累积,在30 μmol/L浓度下不同根段间均达到显著差异,同时品种Hyogo根尖0~2.5 mm和2.5~5.0 mm段铝含量均显著高于品种Alaska,说明品种Alaska和品种Hyogo间存在耐铝性差异,其中品种Alaska耐铝性高于品种Hyogo,即品种Hyogo为铝敏感品种,品种Alaska是耐铝品种。比较两者不同根段(0~2.5 mm、 2.5~5.0 mm和5.0~10.0 mm)的铝含量与果胶含量、 果胶甲基酯化度、 PME活性间的关系,发现耐铝品种不同根段中的铝含量均小于敏感品种,并且在0~2.5 mm和2.5~5.0 mm段间达到显著性差异; 根尖不同根段果胶糖醛酸含量大小依次为0~2.5＞2.5~5.0＞5.0~10.0 mm,耐铝品种Alaska根尖细胞壁果胶和未甲酯化果胶含量均显著低于Hyogo,并且0~2.5 mm根段差异最大。根尖不同根段果胶甲基酯化度从根尖向上逐渐降低,并且耐铝品种Alaska高于铝敏感品种Hyogo,其中0~2.5 mm段间的差异达到显著水平;在对两个品种果胶甲基酯化酶(PME)活性进一步分析发现,PME活性大小依次为0~2.5＞2.5~5.0＞5.0~10.0 mm,两品种0~2.5 mm和2.5~5.0 mm根段间均达到显著差异。【结论】铝敏感品种Hyogo在0~2.5 mm和2.5~5.0 mm根段具有较高 PME活性和较低果胶甲基酯化程度。豌豆根尖果胶含量和甲基酯化度尤其是0~2.5 mm根段是豌豆耐铝性差异的重要原因;Alaska根尖细胞壁的果胶含量低和果胶甲基酯化度高(尤其是0~2.5 mm段)是其耐铝的重要机制。

Differences of pectin content and methylation in root cell wall of pea(Pisum sativum) cultivars with different Al tolerance

【Objectives】 The study investigated the relationship between changes of cell wall pectin, pectin methyl esterification degree and aluminum tolerance in different cultivars of pea (Pisum sativum) to provide theoretical evidences how genetic differences affected aluminum tolerance during plant growth. 【Methods】 All cultivars were cultivated by mist under 24℃growth chamber for 24 h after seed soaking. The root was divided into three segments: 0-2.5 mm, 2.5-5.0 mm and 5.0-10.0 mm. Pectin content, methyl esterification degree and the activity of pectin methylesterase (PME) were measured in differentroot segments of cultivar Hyogo and cultivar Alaska. Relative elongation rate (RER), callose and Al content were also tested to compare Al tolerance in different root zones and cultivars of pea. 【Results】 The RER of Alaska cultivar were significantly higher than Hyogo under Al concentration of 15 μmol/L and 30 μmol/L. And, the callose and Al of 0-5 mm or 5-10 mm segments in Alaska cultivar were accumulated much less than Hyogo. This result confirmed that the Alaska was an Al resistant cultivar and Hyogo was an Al sensitive cultivar. Alaska showed lower Al contents in all segments. In the meantime, the different Al levels between two species were showed significantly in 2.5-5.0 mm and 5.0-10.0 mm segments. Uronic acid content in cell wall pectin was found decreasing sequentially from segment 0-2.5 mm to 5.0-10.0 mm in both pea species. Alaska was measured lower cell wall pectin and un-methylated pectin compared with Hyogo, especially in segment 0-2.5 mm. The activity of PME also decreased successively from segment 0-2.5 mm to 5.0-10.0 mm in both Alaska and Hyogo. The degree of pectin methylation was significantly higher in 0-2.5 mm root segment than the other root segments in Alaska. Alaska had relatively lower content of uronic acid, lower activity of PME, and higher degree of pectin methylation, especially in 0-2.5 mm root segment. 【Conclusions】The key factor for pea cultivars shows Al tolerance or Al sensitive could be pectin content and methylation level in 0-2.5 mm root segment. Hyogo is highly sensitive to Al, which contained higher pectin in 0-2.5 mm root segment. The relatively lower pectin content and high methylation, especially in 0-2.5 mm, of Alaska associated with Al tolerance characterize.