The brown midrib bmr6 and bmr12 mutants of sorghum (Sorghum bicolor) have alterations to the phenylpropanoid pathway impairing the activity of cinnamyl alcohol dehydrogenase (CAD) and/or caffeate5/hydroxyferulate O‐methyl transferase (COMT) enzymes, which inhibit lignin synthesis. Interestingly, these phenylpropanoids can also act as sunscreen compounds in plants and potentially attenuate ultraviolet radiation. We examined the effects of ultraviolet‐B (UV‐B; 280–320 nm) exclusion on growth, cell‐wall constituents and UV‐screening abilities of bmr6, bmr12, a double mutant (bmr6 bmr12; dm) and wild‐type (WT) genotypes of S. bicolor. Plants were grown in a UV‐transparent greenhouse under filters that either transmitted 2.8% (Mylar) or 90% (Aclar) of UV‐B. The greenhouse experiment was a 2 × 4 (UV treatment × genotype) complete factorial design. Sorghum grown under reduced UV were 23% taller and had 22% fewer leaves. Among genotypes, the WT plants were 5%–12% taller than the bmr6, bmr12 and dm mutants. The near‐ambient UV‐B treatment group was more effective at UV screening and had a 16% higher UV‐screening effectiveness than those under reduced UV‐B. Sorghum plants with the bmr6 and dm genotypes had 8%–19% higher UV‐shield than the bmr12 and WT. Plants grown under the reduced UV‐B treatment had 5% less hemicellulose and 6% more cellulose in their cell walls. There were no overall treatment effects on bulk soluble phenolics, chlorophyll fluorescence (Fv/Fm) or lignin concentrations. These results are a possible indication that the bmr mutants of S. bicolor have a varied response to UV‐B exclusion due to alterations in the phenylpropanoid pathway leading to redistribution of metabolites.

中文翻译：

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紫外线 B 应激增加表皮紫外线屏蔽效果并改变二色高粱棕色中脉 bmr6 和 bmr12 突变体的生长和细胞壁成分


高粱（Sorghum bicolor）的棕色中脉 bmr6 和 bmr12 突变体对苯丙素途径发生改变，损害了肉桂醇脱氢酶（CAD）和/或咖啡酸 5/羟基阿魏酸 O-甲基转移酶（COMT）的活性，从而抑制木质素合成。有趣的是，这些苯丙素类化合物还可以充当植物中的防晒化合物，并可能减弱紫外线辐射。我们研究了 UV-B（UV-B；280-320 nm）排除对 bmr6、bmr12、双突变体（bmr6 bmr12；dm）和野生型（bmr6 bmr12；dm）的生长、细胞壁成分和紫外线屏蔽能力的影响。 WT) 双色链球菌的基因型。植物生长在紫外线透明温室中，过滤器可透射 2.8%（Mylar）或 90%（Aclar）的 UV-B。温室实验是2×4（紫外线处理×基因型）完全析因设计。在减少紫外线的条件下生长的高粱高了 23%，叶子减少了 22%。在基因型中，WT植株比bmr6、bmr12和dm突变体高5%–12%。接近环境的 UV-B 治疗组在紫外线筛查方面更有效，并且比减少 UV-B 治疗组的紫外线筛查效果高 16%。具有 bmr6 和 dm 基因型的高粱植物的紫外线屏蔽能力比 bmr12 和 WT 高 8%–19%。在减少 UV-B 处理下生长的植物细胞壁中的半纤维素减少了 5%，纤维素增加了 6%。总体处理对大量可溶性酚类物质、叶绿素荧光 (Fv/Fm) 或木质素浓度没有影响。这些结果可能表明，S. bicolor 的 bmr 突变体由于苯丙素途径的改变导致代谢物重新分布，对 UV-B 排除具有不同的反应。