Birecka H
Department of Biological Sciences, Union College, Schenectady, New York 12308.
Plant Physiol. 1978 Apr;61(4):561-6. doi: 10.1104/pp.61.4.561.
Mechanical injury or infection with Helminthosporium maydis race T or O enhanced peroxidase activity in leaves of two corn inbreds which differ in their susceptibility to the fungal race T. Increases in activity were found in the soluble fraction extracted from tissues with 20 mm phosphate buffer (pH 6), and in the ionically bound fraction extracted from wall debris with 0.6 to 1 m NaCl; the covalently bound wall peroxidase fraction was unaffected. Mechanical injury and infection with either race enhanced the same distinctive cathodic isoforms present in the soluble fraction or in both the soluble and ionically bound fractions.During the first 20 to 22 hours after inoculation no differences were found in the enzyme enhancement in relation either to the corn line or fungal race. During the second day, the weaker the infection symptoms, the greater was the peroxidase enhancement. The race T-infected susceptible inbred showed no increase or a decrease in the enzyme activity, whereas in most cases both inbreds infected with race O exhibited a further peroxidase enhancement.Pretreatment of healthy leaves or leaf discs with cycloheximide at concentrations which did not cause a loss of turgor had no effect on peroxidase enhancement. However, in tissues inoculated with either the race T or O, cycloheximide, at concentrations which did not affect the mechanical injury-induced increase in peroxidase activity, did inhibit the enzyme enhancement and did cause a loss of turgor.The observed changes in isoperoxidase activities (a) confirm the assumption that the infection-induced enhancement of this enzyme results from a nonspecific response to injury; (b) support the postulation that the often observed small or no increases in peroxidase activity to compatible hosts are a consequence of metabolic disorders rather than the cause of a lower resistance; and (c) indicate that cycloheximide as a protein synthesis inhibitor may increase the compatibility between the host and pathogen, enhance metabolic disorders in inoculated tissues, and in consequence interfere with the nonspecific cell response to injury.Actinomycin D did not affect the mechanical injury- or infection-induced peroxidase enhancement. Neither did ethylene at 5 to 80 mul/l have a significant effect on the enzyme activity in healthy, injured, or infected tissues.
机械损伤或感染玉米小斑病菌T小种或O小种会增强两个玉米自交系叶片中的过氧化物酶活性，这两个自交系对T小种真菌的易感性不同。在用20 mM磷酸盐缓冲液（pH 6）从组织中提取的可溶部分以及用0.6至1 M NaCl从细胞壁碎片中提取的离子结合部分中发现活性增加；共价结合的细胞壁过氧化物酶部分未受影响。机械损伤和任何一种小种的感染都会增强可溶部分或可溶部分与离子结合部分中相同的独特阴极同工型。在接种后的最初20至22小时内，在酶增强方面，无论是玉米品系还是真菌小种，均未发现差异。在第二天，感染症状越轻，过氧化物酶增强的程度就越大。感染T小种的易感自交系酶活性没有增加或有所下降，而在大多数情况下，感染O小种的两个自交系过氧化物酶都进一步增强。用不会导致细胞膨压丧失的浓度的环己酰亚胺预处理健康叶片或叶盘，对过氧化物酶增强没有影响。然而，在用T小种或O小种接种的组织中，环己酰亚胺在不影响机械损伤诱导的过氧化物酶活性增加的浓度下，确实抑制了酶的增强，并且确实导致了细胞膨压丧失。观察到的同功过氧化物酶活性变化：（a）证实了这样的假设，即感染诱导的这种酶的增强是对损伤的非特异性反应的结果；（b）支持这样的推测，即经常观察到的对亲和寄主过氧化物酶活性很少增加或没有增加是代谢紊乱的结果，而不是抗性较低的原因；（c）表明环己酰亚胺作为蛋白质合成抑制剂可能会增加寄主与病原体之间的亲和性，增强接种组织中的代谢紊乱，从而干扰细胞对损伤的非特异性反应。放线菌素D不影响机械损伤或感染诱导的过氧化物酶增强。5至80 μl/l的乙烯对健康、受伤或感染组织中的酶活性也没有显著影响。
