BACKGROUND Handedness in plants introduced by helical growth of organs is frequently observed, and it has fascinated plant scientists for decades. However, the genetic control of natural handedness has not been revealed. In the model legume Medicago truncatula, pods can be coiled in a clockwise or anti-clockwise manner, providing a model for genetic analysis of plant handedness. OBJECTIVE We aimed to localize the Sense of Pod Coiling (SPC) gene controlling pod coiling direction in M. truncatula. METHODS Linkage analysis was used with a biparental population for fine mapping of the SPC gene. The genome sequence of M. truncatula Mt4.0 was used for marker identification and physical mapping. Single nucleotide polymorphisms (SNPs) between the parental lines were converted to CAPS (cleaved amplified polymorphic sequences) markers. Genetic map was constructed using the software JoinMap version 3.0. Gene predication and annotation provided by the M. truncatula genome database (http://www.medicagogenome.org) was confirmed with the programs of FGENESH and Pfam 32.0, respectively. Quantitative reverse transcription PCR (qRT-PCR) was used to analyze the relative expression levels of candidate genes. RESULTS The genetic analysis indicated that the anti-clockwise coiling is dominant to clockwise and is controlled by the single gene, SPC. The SPC gene was delimited to a 250 kb-region on Chromosome 7. Total of 15 protein-coding genes were identified in the SPC locus through gene annotation and sequence analysis. Of those, two genes, potentially encoding a receptor-like kinase and a vacuolar cation/proton exchanger respectively, were selected as candidates for the SPC gene. CONCLUSIONS The result presented here lay a foundation for gene cloning of SPC, which will help us to understand the molecular mechanisms underlying helical growth in plant organs.

中文翻译：

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SPC基因的遗传定位控制Medi藜的荚果盘绕方向。

背景技术经常观察到由器官的螺旋状生长引入的植物中的手感，并且数十年来一直使植物科学家着迷。但是，自然手性的遗传控制尚未揭示。在豆科植物紫花苜蓿模型中，可以按顺时针或逆时针方式缠绕豆荚，从而为植物遗传习惯的遗传分析提供了一个模型。目的我们的目的是定位控制荚果卷心菜豆荚卷曲方向的豆荚卷曲感（SPC）基因。方法将连锁分析与双亲种群一起用于SPC基因的精细定位。截短支原体Mt4.0的基因组序列用于标记鉴定和物理作图。亲本系之间的单核苷酸多态性（SNP）被转换为CAPS（裂解扩增多态序列）标记。遗传图谱是使用JoinMap 3.0版软件构建的。truncatula基因组数据库（http://www.medicagogenome.org）提供的基因预测和注释分别通过FGENESH和Pfam 32.0程序进行了确认。定量逆转录PCR（qRT-PCR）用于分析候选基因的相对表达水平。结果遗传分析表明，逆时针卷曲比顺时针占优势，并且受单个基因SPC控制。SPC基因在染色体7上被定界为250 kb区域。通过基因注释和序列分析，在SPC基因座中总共鉴定出15个蛋白质编码基因。其中，选择两个可能分别编码受体样激酶和液泡阳离子/质子交换剂的基因作为SPC基因的候选基因。