It has been hypothesized that under iron stress high ferric chelate reductase (FCR) activity in the absorptive root of plants tolerant to iron deficiency will be induced and result in subsequent Fe2+ transport across the plasmalemma. The activity of FCR and expression of FCR gene ( FRO2 ) in Citrus junos Sieb. ex Tanaka tolerant to iron deficiency and Poncirus trifoliata(L.) Raf. susceptible to iron deficiency were determined to elucidate the physiological difference which causes the different tolerance of the two citrus rootstocks to iron stress. The activity of FCR was detectable in excised roots and was stimulated about 20 times in C. junos and only about 3 times in P. trifoliata under iron deficiency for four weeks. The FRO2 of Arabidopsis was used as a probe, the tissue print technique was used to ascertain the expression of the FCR gene in C. junos and P. trifoliata under iron stress. High level transcripts were observed in the absorptive root, young green stem as well as new leaf of C. junos under iron stress for two weeks, and the transcripts were accumulated only slightly in P. trifoliata at the same time. The results showed that the obvious increase of FCR activity was an important reason for the tolerance of C. junos to iron deficiency, and the regulation of FCR activity seemed to be at the transcriptional level, and the expression of FRO2 occurred in the root, stem and leaf.
三价铁螯合物还原酶在香橙和枳中的表达
李 凌 范艳华 罗小英 裴 炎 周泽扬*
（西南农业大学生物技术中心，重庆400716）
摘要: 用耐缺铁的香橙 (Citrusjunos Sieb .exTanaka)和极不耐缺铁的枳 (Poncirustrifoliata (L .)Raf.) ,在铁胁迫条件下对根的三价铁螯合物还原酶活性变化和酶基因的表达情况进行了研究。离体根的酶活性测定表明 ,在铁胁迫 4周时 ,香橙根的酶活性增强约 2 0倍 ,枳仅增强约 3倍。用拟南芥的三价铁螯合物还原酶基因作探针进行组织印迹的Northern杂交检测香橙和枳三价铁螯合物还原酶的mRNA ,在铁胁迫 2周时 ,香橙吸收根、幼茎和新叶中均检测到强烈的表达信号 ,而枳相同器官的表达信号则极其微弱。实验结果表明 ,三价铁螯合物还原酶活性在缺铁胁迫下被诱导强烈增加是香橙耐缺铁的重要原因 ,该酶活性的调控发生在转录水平上 ,而且该酶基因在诱导条件下在根、茎和叶中均有表达。
关键词： 香橙；枳；缺铁胁迫；三价铁螯合还原酶；组织印迹；FR02基因
通讯作者。E-mail: <zyzhou @ swau.edu.cn>.
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