English Bethany, Quinn Alicia A, Warren Charles R, Gleadow Roslyn M, Myrans Harry
School of Biological Sciences, Monash University, Clayton, Vic 3800, Australia.
School of Life and Environmental Sciences, The University of Sydney, Camperdown, NSW 2006, Australia.
Funct Plant Biol. 2025 Apr;52. doi: 10.1071/FP24343.
Sorghum (Sorghum bicolor [L.] Moench) is an important forage crop that contains the cyanogenic glucoside dhurrin that releases hydrogen cyanide when tissue is damaged. The acyanogenic (dhurrin-free) sorghum line tcd1 was developed to eliminate the risk of cyanide poisoning from sorghum forage. However, dhurrin may also play a role in nitrogen accumulation and storage. We tested whether dhurrin offers the cyanogenic sorghum line BTx623 a growth advantage relative to tcd1 , when nitrogen is limiting and variable. BTx623 and tcd1 were grown under two 42-day nitrogen treatments: high dose, low frequency ('surge') and low dose, high frequency ('pulse'). BTx623 exhibited no growth advantage or disadvantage compared to tcd1 under either treatment. Young BTx623 plants had high concentrations of dhurrin for defence but rapidly recycled this during nitrogen deficiency under the surge treatment, demonstrating dhurrin's role in both defence and nitrogen storage. At later stages, surge plants appeared to accumulate influxes of nitrogen in nitrate and amino acids but not dhurrin. There was evidence of gene expression promoting increased biosynthesis and reduced recycling of dhurrin following surge nitrogen applications but not pulse applications. These results deepen our understanding of dhurrin's role in nitrogen metabolism and demonstrate tcd1 's potential as a safe forage.
高粱（Sorghum bicolor [L.] Moench）是一种重要的饲料作物，含有生氰糖苷蜀黍苷，当组织受损时会释放出氰化氢。为消除高粱饲料氰化物中毒风险，培育出了无氰（无蜀黍苷）高粱品系tcd1。然而，蜀黍苷可能也在氮素积累和储存中发挥作用。我们测试了在氮素有限且多变的情况下，蜀黍苷是否能为含氰高粱品系BTx623提供相对于tcd1的生长优势。BTx623和tcd1在两种为期42天的氮处理下生长：高剂量、低频率（“激增”）和低剂量、高频率（“脉冲”）。在两种处理下，BTx623与tcd1相比均未表现出生长优势或劣势。年轻的BTx623植株含有高浓度的蜀黍苷用于防御，但在激增处理下氮素缺乏时会迅速将其循环利用，这表明蜀黍苷在防御和氮储存中都发挥作用。在后期，激增处理的植株似乎在硝酸盐和氨基酸中积累了氮素流入，但没有积累蜀黍苷。有证据表明，在激增施氮后而非脉冲施氮后，基因表达促进了蜀黍苷生物合成增加和循环利用减少。这些结果加深了我们对蜀黍苷在氮代谢中作用的理解，并证明了tcd1作为安全饲料的潜力。
