The isolation of flowering time genes from lettuce to enable the manipulation of bolting time
The isolation of flowering time genes from lettuce to enable the manipulation of bolting time
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发表时间：
2010-09
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通讯作者：
A. Abbott
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作者：
A. Abbott
抽薹时间是莴苣生产中的一个重要因素，因为它影响收获作物的产量和质量。较高的温度促进了抽薹，随着目前夏季变暖的趋势，抽薹对种植者来说是一个越来越大的问题。处于抽薹早期阶段的莴苣植物与非抽薹植物明显无法区分，然而，产生的次生代谢物的生物合成发生了变化，以保护幼花芽免受昆虫攻击。这些化合物给莴苣植物带来苦味，使作物无法销售。晚抽薹品种的发展，这将有一个更大的'持有能力'在外地，将导致减少作物损失和延长生长季节。在许多植物中，从营养生长到开花的过渡时间由环境线索控制，这些环境线索用于传达有利于有性生殖和种子成熟的生长条件。对拟南芥的研究已经鉴定出几种不同的途径，它们共同调节开花时间。关于生菜中这些反应途径的研究很少，然而，研究表明这些途径的组成部分在拟南芥和其他作物物种之间是保守的。本项目的目的是分离调控莴苣开花时间的基因，以便这些基因的新等位基因可用于操纵抽薹时间。莴苣BAC库已筛选和同源的8个拟南芥开花时间基因，主要是从自主途径，已被分离。在莴苣中已经鉴定了FLOWERLOCUS T（FT）和自主途径基因FLK的功能性直向同源物，这表明在拟南芥和莴苣中涉及开花时间的基因是保守的。具有一系列抽薹时间的莴苣系，包括比野生型显著晚抽薹的系，已经从EMS诱变的栽培莴苣群体和野生莴苣的多样性组中鉴定出。来自莴苣cv。拉里萨EMS人口具有可重复的晚抽薹表型时，在商业化的生长条件下进行了测试已被确定。这些品系已经提供给Rijk Zwaan®，用于未来的育种计划，旨在延迟抽薹和提高商业莴苣作物的“保持能力”。选择生菜开花时间基因的基因组序列进行了比较晚抽薹线和野生型之间寻找多态性，可能会导致晚抽薹表型。在这些基因内的多态性被确定在一些晚抽薹线，然而，通过分析分离回交群体中的多态性，他们已被证明不会导致晚抽薹表型。还进行了转录组测序以鉴定可能引起晚抽薹表型的其他可能新的基因中的多态性，迄今为止，尚未鉴定出晚抽薹品系内的突变分离。
The time of bolting is an important factor in lettuce production because it affects the yield and quality of the harvested crop. Bolting is promoted by higher temperatures and is an increasing problem for growers with the current trend for warmer summers. Lettuce plants that are in the early stages of bolting are visibly indistinguishable from non-bolting plants, however there are changes in the biosynthesis of secondary metabolites which are produced to protect the young floral bud from insect attack. These compounds give the lettuce plant a bitter taste and render the crop unsaleable. The development of late bolting varieties, which would have a greater ‘holding ability’ in the field, would result in reduced crop losses and an extension to the growing season. In many plants, the timing of the transition from vegetative growth to flowering is controlled by environmental cues which serve to communicate growth conditions favourable for sexual reproduction and seed maturation. Studies in Arabidopsis have led to the identification of several different pathways that come together to regulate flowering time. Little research has been done on these response pathways in lettuce, however, research has shown that components of these pathways are conserved between Arabidopsis and other crop species. The aim of this project is to isolate genes regulating flowering time in lettuce in order that novel alleles of these genes can be used to manipulate bolting time. A lettuce BAC library has been screened and homologues of eight Arabidopsis flowering time genes, principally from the autonomous pathway, have been isolated. Functional orthologues of FLOWERING LOCUS T (FT) and the autonomous pathway gene, FLK have been characterised in lettuce, suggesting that there is conservation of the genes involved in flowering time in Arabidopsis and lettuce. Lettuce lines with a range of bolting times, including lines which bolt significantly later than wild-type have been identified from EMS mutagenised populations of cultivated lettuce and a diversity set of wild lettuce. Homozygous lines from a Lactuca sativa cv. Larissa EMS population with a reproducible late bolting phenotype when tested under commercial growing conditions have been identified. These lines have been made available to Rijk Zwaan® for inclusion in future breeding programs aimed at delaying bolting and improving the ‘holding’ ability’ of commercial lettuce crops. Genomic sequence of selected lettuce flowering time genes have been compared between the late bolting lines and wild-type looking for polymorphisms that may account for the late bolting phenotype. Polymorphisms within these genes were identified in some of the late bolting lines, however through analysing the polymorphism in segregating backcross populations they have been shown not to be causing the late bolting phenotype. Transcriptome sequencing has also been performed to identify polymorphisms in other, possibly novel, genes which may be causing the late bolting phenotype, as yet, no mutation segregating within the late bolting lines has been identified.