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以长中胚轴玉米自交系PH4CV为材料,在黑暗和光照两种处理条件下研究了玉米中胚轴长度与多胺氧化酶(polyamine oxidase,PAO)活性、H_2O_2含量、过氧化物酶(peroxidase,POD)活性及木质素含量的关系。通过添加5 mmol L~(–1) PAO抑制剂2-羟乙基肼(2-hydroxyethylhydrazine,2-HEH)和5 mmol L~(–1) H_2O_2清除剂N,N’-二甲基硫脲(N,N’-Dimethylthiourea,DMTU)及组织化学染色,研究了影响中胚轴伸长的H_2O_2来源及其积累部位。采用实时荧光定量PCR(q RT-PCR)方法,探究了光对Zm PAO基因表达的影响。结果表明,光照处理显著抑制了玉米中胚轴的伸长,同时显著增加该部位的PAO活性、H_2O_2含量、POD活性及木质素含量。相关性分析表明,玉米中胚轴长度与PAO活性、H_2O_2含量和木质素含量呈极显著负相关,与POD活性呈显著负相关;PAO活性与H_2O_2含量、POD活性和木质素含量均呈正相关。外源PAO抑制剂和H_2O_2清除剂处理试验,玉米中胚轴表皮纵切面细胞长度显微观察及中胚轴H_2O_2组织化学染色表明,PAO氧化分解多胺(polyamines,PAs)产生的H_2O_2参与了中胚轴细胞伸长的生理调控,从而抑制了中胚轴的伸长。表达分析表明,Zm PAO基因在黑暗环境下的表达量相对稳定,光刺激0.5 h后表达量迅速升高,3 h后达到最大值,随后逐渐下降,10 h后趋于稳定。本研究表明,PAO在接受光刺激后活性升高,氧化分解PAs产生H_2O_2,从而诱导POD氧化胞壁的单木质醇并聚合为木质素,使细胞壁硬化,造成细胞伸长受阻。研究结果为进一步探讨PAO活性调控光诱导玉米中胚轴伸长的生理机制和阐明玉米中胚轴对光逆境的响应机理提供了理论依据。
The mesophyll length, the polyamine oxidase (PAO) activity, the content of H 2 O 2, the activity of peroxidase peroxidase, POD activity and lignin content. By adding 5 mmol L -1 PAO inhibitor 2-hydroxyethylhydrazine (2-HEH) and 5 mmol L -1 H 2 O 2 scavenger N, N’-dimethylthiourea (N, N’-Dimethylthiourea, DMTU) and histochemical staining were used to study the source and accumulation of H 2 O 2 affecting the mesocotyl elongation. Real-time fluorescent quantitative PCR (q RT-PCR) method was used to investigate the effect of light on Zm PAO gene expression. The results showed that light treatment significantly inhibited the elongation of mesocotyl in maize, and significantly increased PAO activity, H 2 O 2 content, POD activity and lignin content in this area. Correlation analysis showed that the mesocotyl length of maize had extremely significant negative correlation with PAO activity, H 2 O 2 content and lignin content, but negatively correlated with POD activity. PAO activity had a positive correlation with H 2 O 2 content, POD activity and lignin content. Exogenous PAO inhibitor and H 2 O 2 scavenger treatment experiments, microscopic observation of mesocotyl cuticle length and H 2 O 2 histochemical staining showed that PAO oxidatively decomposed polyamines (PAs) produced by H 2 O 2 Physiological regulation of hypocotyls cell elongation, thus inhibiting the mesocarp elongation. Expression analysis showed that the expression of Zm PAO gene in dark environment was relatively stable, and the expression of Zm PAO gene rapidly increased after 0.5 h of light stimulation and reached its maximum at 3 h, then decreased gradually and stabilized at 10 h. The present study shows that after being stimulated by light, PAO is activated to oxidatively decompose PAs to produce H 2 O 2, thereby inducing POD to oxidize single-cell lignin in the cell wall and polymerize into lignin, which hardens the cell wall and hinders cell elongation. The results provide theoretical basis for further exploring the physiological mechanism of PAO activity regulating light-induced elongation of mesocotyl in maize and elucidating the response mechanism of corn mesocotyl to light stress.