Acquisition of a New Regulatory System by a Ds Transposon in Maize

9507612玉米蜡质(Wx)基因3个相关等位基因间的遗传距离。每一个都是由2kb的D插入到完全相同的位置引起的，一个等位基因WX-M5：CS7((DS)(CS7))，生殖性回复比另外两个少90倍，尽管所有三个等位基因在胚乳中表现出相同的频繁的体细胞回复。CS7生发逆转的抑制在遗传上与Wx有关，与转座酶来源无关，并且不抑制其他座位上DS插入的切除，这表明顺式作用突变使CS7 D受到一种新型的发育控制。这一建议检验的总体假设是，由于CS7D的突变，寄主植物现在可以通过在发育上限制转座子与适当的转座酶结合的程度来抑制转座子。具体来说：1.对SD7、CS8和CS8311B中的DS元件进行测序和比较；2.比较DNA甲基化并量化植物发育过程中不同阶段的剪切率；3.通过检测CS7/CS8杂合子中CS7生发逆转的抑制作用来检验DS元件之间的相互作用；4.鉴定控制CS7切割的顺式和反式作用因素；5.鉴定与CS7和CS8不同的DS结合的玉米蛋白。这项研究的目标是通过研究植物调节转座子活性的机制以及它们如何相互作用来了解植物的遗传控制机制。插入玉米基因组相同位置的三个转座子具有不同的生发切除频率，尽管这些频率在体细胞中是相同的。将启动研究，以确定玉米植株中控制这种差异的机制。这些研究将有助于更全面地了解调控基因表达的因子，以及更深入地了解植物寄主因子在转座中的参与。***

9507612 Weil Among three related alleles of the maize waxy (Wx) gene. each caused by a 2 kilobase Ds insertion into precisely the same site, one allele, wx-m5:CS7 ((Ds) (CS7), reverts germinally as much as 90 fold less than the other two even though all three alleles show the same frequent, somatic reversion in the endosperm. The suppression of CS7 germinal reversion is genetically linked to Wx, independent of the transposase source and does not suppress excision by Ds insertions at other loci, suggesting a cis-acting mutation subjecting the CS7 Ds to a novel type of developmental control. The overall hypothesis tested in this proposal is that, because of a mutation in the CS7 Ds, the host plant can now suppress this transposon by developmentally restricting how accessible it is to proper transposase binding. Specifically: 1. The Ds elements in SD7, CS8, and CS8311B will be sequenced and compared, 2. DNA methylation will be compared and the excision rate quantitated at different stages during plant development, 3. The interaction of the DS elements will be tested by assaying the suppressiol of CS7 germinal reversion in CS7/CS8 heterozygotes, 4. cis- and trans-acting factors controlling CS7 excision will be identified and 5. maize proteins that bind the CS7 Ds and the CS8 Ds differently will be identified. %%% The goal of this research is to understand genetic control mechanisms in plants by examining mechanisms whereby plants regulate transposable element activity and how they interact with each other. Three transposons of corn which have inserted into identical positions on the corn genome have different germinal excision frequencies although such frequencies are identical in somatic cells. Studies will be initiated to determine the mechanisms controlling such differences in the corn plant. These studies will contribute to a more general understanding of factors regulating gene expression as well as allowing more insight into the participation of plant host factors in transposition. ***