Data_Sheet_1_Elucidating Mitochondrial DNA Markers of Ogura-Based CMS Lines in Indian Cauliflowers (Brassica oleracea var. botrytis L.) and Their Floral Abnormalities Due to Diversity in Cytonuclear Interactions.docx

Mitochondrial markers can be used to differentiate diverse mitotypes as well as cytoplasms in angiosperms. In cauliflower, cultivation of hybrids is pivotal in remunerative agriculture and cytoplasmic male sterile lines constitute an important component of the hybrid breeding. In diversifying the source of male sterility, it is essential to appropriately differentiate among the available male sterile cytoplasms in cauliflower. PCR polymorphism at the key mitochondrial genes associated with male sterility will be instrumental in analyzing, molecular characterization, and development of mitotype-specific markers for differentiation of different cytoplasmic sources. Presence of auto- and alloplasmic cytonuclear combinations result in complex floral abnormalities. In this context, the present investigation highlighted the utility of organelle genome-based markers in distinguishing cytoplasm types in Indian cauliflowers and unveils the epistatic effects of the cytonuclear interactions influencing floral phenotypes. In PCR-based analysis using a set of primers targeted to orf-138, 76 Indian cauliflower lines depicted the presence of Ogura cytoplasm albeit the amplicons generated exhibited polymorphism within the ofr-138 sequence. The polymorphic fragments were found to be spanning over 200–280 bp and 410–470 bp genomic regions of BnTR4 and orf125, respectively. Sequence analysis revealed that such cytoplasmic genetic variations could be attributed to single nucleotide polymorphisms and insertion or deletions of 31/51 nucleotides. The cytoplasmic effects on varying nuclear-genetic backgrounds rendered an array of floral abnormalities like reduction in flower size, fused flowers, splitted style with the exposed ovule, absence of nonfunctional stamens, and petaloid stamens. These floral malformations caused dysplasia of flower structure affecting female fertility with inefficient nectar production. The finding provides an important reference to ameliorate understanding of mechanism of cytonuclear interactions in floral organ development in Brassicas. The study paves the way for unraveling developmental biology of CMS phenotypes in eukaryotic organisms and intergenomic conflict in plant speciation.

线粒体标记（mitochondrial markers）可用于区分被子植物（angiosperms）中多样的线粒体型（mitotypes）与细胞质。花椰菜（cauliflower）的杂交栽培是盈利性农业（remunerative agriculture）的核心环节，而细胞质雄性不育系（cytoplasmic male sterile lines）是杂交育种（hybrid breeding）的重要组成部分。在拓宽雄性不育（male sterility）种质来源的工作中，精准区分花椰菜现有各类雄性不育细胞质极为关键。与雄性不育相关的关键线粒体基因的聚合酶链式反应（PCR）多态性，将为分析、分子鉴定以及开发用于区分不同细胞质来源的线粒体型特异性标记（mitotype-specific markers）提供重要支撑。自体与异质细胞质核组合（auto- and alloplasmic cytonuclear combinations）会引发复杂的花发育异常（floral abnormalities）。在此背景下，本研究阐明了基于细胞器基因组的标记在区分印度花椰菜细胞质类型中的应用价值，并揭示了影响花表型（floral phenotypes）的细胞质核互作上位效应（epistatic effects）。在以靶向orf-138的引物开展的PCR分析中，76份印度花椰菜材料均扩增出Ogura细胞质特征条带，但所得扩增产物（amplicons）在orf-138序列内存在多态性。研究发现，这些多态性片段分别对应BnTR4基因200–280 bp的基因组区域以及orf125基因410–470 bp的基因组区域。序列分析表明，这类细胞质遗传变异可归因于单核苷酸多态性（single nucleotide polymorphisms）以及31/51个核苷酸的插入或缺失（insertion or deletions）。细胞质对不同核遗传背景（nuclear-genetic backgrounds）的影响，引发了一系列花发育异常表型，包括花尺寸减小、花器官融合、花柱开裂且胚珠外露、无功能雄蕊缺失以及花瓣状雄蕊（petaloid stamens）。此类花畸形会导致花结构发育不良，同时伴随花蜜分泌（nectar production）不足，进而影响雌性育性（female fertility）。本研究结果为加深对芸苔属（Brassicas）植物花器官发育过程中细胞质核互作机制的理解提供了重要参考。本研究还为解析真核生物的细胞质雄性不育（Cytoplasmic Male Sterility, CMS）表型的发育生物学机制以及植物物种形成（plant speciation）过程中的基因组间冲突（intergenomic conflict）开辟了新的研究路径。