外源基因在一个转基因水稻四倍体变异株系中的遗传行为

在基因枪介导转化的转基因水稻植株中发现1个四倍体变异株系XIP-4N．该变异株系T₀代植株中转基因的整合模式与二倍体转基因株系XIP-2N相同，并且二者来自同一转化体系，推测XIP-4N株系是转化后的水稻愈伤组织在细胞有丝分裂过程中发生染色体加倍产生的．对外源筛选标记基因bar和非筛选基因cecropinB在转基因株系XIP-4N和XIP-2N中的遗传行为进行了比较研究．在二倍体转基因株系XIP-2N中,bar和cecropinB基因的Southern整合模式从T₀到T₂代遗传稳定，单位点整合的bar基因按孟德尔单基因显性方式向后代传递．四倍体转基因株系XIP-4N中外源基因遗传行为复杂，单位点整合的bar基因（Basta抗性）T₁代按15∶1分离，T₂和T₃代中分离行为复杂，而且bar和cecropinB基因的整合模式遗传不稳定．同源四倍体水稻植株减数分裂过程中染色体结构变异、转基因相关位点DNA片段的遗传重组与修饰，以及由此导致配子的育性降低，可能是导致外源基因遗传行为复杂的主要原因．转基因四倍体水稻变异株系XIP-4N携带易于检测的bar基因，为研究同源四倍体水稻的遗传和生殖机理提供了好材料．

Heredity of the Exotic Genes in a Tetraploid Transgenic Rice Variant

A tetraploid transgenic rice line XIP-4N was obtained from particle bombardment transformation. The T₀ plant of this variant exhibited the same transgenic integration patterns to that of XIP-2N, another diploid line, derived fromthe same transformation approach, indicating that XIP-4N was resulted from chromosome doubling during the course of mitosis. We compared the hereditary behaviors of a exotic selected marker gene bar (Basta resistance) with a non-selected gene cecropin B in XIP-4N and XIP-2N by Southern blot analysis. Both bar and cecropin B gene were stably inherited in XIP-2N from T₀ to T₂ generation, whereas the heredity of the exotic genes in XIP-4N was rather complex, which both bar and cecropin B appeared to be unstable. The bar gene, which integrated as a single locus in rice genome and transferred to offspring plants as a dominant gene according to Mendel law in XIP-2N, segregated at a 15∶1 ratio in T₁ generation, and started to be complicated in T₂ and T₃ generations of XIP-4N. We speculated the causes for the complex transgene hereditary behaviours of the tetraploid variant XIP-4N involved variations of chromosome structures, genetic recombinations, modifications of the DNA fragments related to the transgenic loci during meiosis and the subsequently decreased the gamete fertility. The XIP-4N tetraploid variant carrying the exotic bar gene may provide an easy-testing material for studying the genetic structure and the reproduction of autotetraploid rice.