Interactions of the mannose-binding rice lectin with sugar chains of ConA-binding glycoproteins secreted by rice blast fungus

甘露糖结合水稻凝集素（MRL）是在干旱、病害和创伤等胁迫下产生的。MRL具有凝集大孔菌孢子和原生质体以及米黄单胞菌完整细胞的潜在活性，并在侵染部位周围积累。MRL由一些分离素组成；2个主要的有4.85和4.74，小的有4.66、4.56和4.44，而所有的都有大约15000个单肽。我们已经分离并鉴定了与pI4.85对应的主要一株，命名为MRL4.85。对MRL4.85基因和基因组结构的分析表明：(1)MRL4.85基因与水稻盐胁迫和干旱胁迫诱导的salt基因产物几乎相同；(2)MRL4.85基因通过选择性剪接转录成至少5个mrna；(3)调控MRL4.85转录本的5′-UTR长度不同，且在其中一个salT基因中缺少含有2个多核苷酸的部分序列。进一步通过BAG文库筛选和水稻基因组计划数据表明，MRL4.85基因位于水稻植株的第一条染色体上，在MRL4.85上游约130kb处存在与分离素相对应的类似序列。为了验证MRL可能在宿主-寄生虫相互作用中作为植物抗体或受体发挥作用的假设，我们试图利用整合了正链或负链CaMV 35S启动子的二元载体pC1304E，获得水稻植株过度表达或抑制MRL4.85产物的转化子。在愈伤组织水平上获得了10个左右的转化体。利用Con A亲和层析和高效液相色谱法纯化了稻瘟病菌萌发分生孢子分泌的Con A结合糖蛋白，该蛋白可能与MRL相互作用，并具有促进植物感染菌丝附着胞形成和生长的活性。主要的糖蛋白是mw28k，在许多AA残基上被糖链修饰，证明不是通过n糖基化，而是通过o糖基化。少

The mannose-binding rice lectin (MRL) is induced by some stresses of drought, disease and wound. MRL has a potential activity to agglutinate spores and protoplasts of Magnaporthe girisea and also intact cells of Xanthomonas oryzae, and also accumulated around the infection sites. MRL is composed of some isolectins ; 2 major ones have pi 4.85 and 4.74, the minor pi 4.66, 4.56, and 4.44, whereas all ones have about MW 15,000 as a single peptide. We have already isolated and identified the major one corresponding to pI4.85, named MRL4.85. Analysis of the MRL4.85 gene and the genome structures suggested that (1) MRL4.85 is almost identical to salt and drought stress-inducible salT gene products in rice plant, (2) MRL4 85 gene is transcribed to at least 5 mRNAs by alternative splicing ; one lacks 8 amino acid residues without flame | shift and the other differ in the length of 3'-UTR, (3) the 5'-UTR regulating the transcripts of MRL4.85 differs in length and lack the part of sequence contai … More ned in one of the salT gene. Further, screening of BAG library and the data of the rice genome project suggested that MRL4.85 gene is located at the first chromosome in rice plant and the similar sequence corresponding to an isolectin exists at about 130kb upstream of MRL4.85.To verify our hypotheses that MRL may function as plant antibodies or receptors in host-parasite interaction, we have tried to obtain the transformants of rice plant to express excessively or suppressively the MRL4.85 product, using the binary vector pC1304E with CaMV 35S promoter in which the positive or negative strands are integrated. And some ten transformants are obtained at callus level.Con A-binding glycoproteinis secreted from germinating conidia of M. grisea, which potentially interact with MRL and have activity to promote appressorium formation and growth of infection hyphae in planta, are purified by Con A affinity chromatography and HPLC. The major glycoprotein is MW 28k and modified by sugar chains at many AA residues, provably not by N-glycosylation but by O-glycosylation. Less