Department of Agronomy Food Natural Resources Animals and Environment (DAFNAE), University of Padova, Campus of Agripolis, Viale dell'Università 16, 35020 Legnaro, PD, Italy.
Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy.
Int J Mol Sci. 2020 Jun 30;21(13):4664. doi: 10.3390/ijms21134664.
Cytoplasmic male sterility (CMS) has always aroused interest among researchers and breeders, being a valuable resource widely exploited not only to breed F1 hybrid varieties but also to investigate genes that control stamen and pollen development. With the aim of identifying candidate genes for CMS in fennel, we adopted an effective strategy relying on the comparison between mitochondrial genomes (mtDNA) of both fertile and sterile genotypes. mtDNA raw reads derived from a CMS genotype were assembled in a single molecule (296,483 bp), while a draft mtDNA assembly (166,124 nucleotides, 94 contigs) was performed using male fertile sample (MF) sequences. From their annotation and alignment, two -like sequences were identified. , the putative mutant copy with a 300 bp truncation at the 5'-end, was found only in the mtDNA of CMS samples, while the wild type copy () was detected only in the MF mtDNA. Further analyses (i.e., reads mapping and Sanger sequencing), revealed an copy also in CMS samples, probably in the nuclear DNA. However, qPCRs performed on different tissues proved that, despite its availability, is expressed only in MF samples, while mRNA was always detected in CMS individuals. In the light of these findings, the energy deficiency model could explain the pollen deficiency observed in male sterile flower. could represent a gene whose mRNA is translated into a not-fully functional protein leading to suboptimal ATP production that guarantees essential cellular processes but not a high energy demand process such as pollen development. Our study provides novel insights into the fennel mtDNA genome and its genes, and paves the way for further studies aimed at understanding their functional roles in the determination of male sterility.
细胞质雄性不育（CMS）一直引起研究人员和育种者的兴趣，是一种广泛利用的有价值的资源，不仅用于培育 F1 杂交品种，还用于研究控制雄蕊和花粉发育的基因。为了在茴香中鉴定 CMS 的候选基因，我们采用了一种有效的策略，依赖于可育和不育基因型的线粒体基因组（mtDNA）之间的比较。源自 CMS 基因型的 mtDNA 原始读数被组装成单个分子（296,483bp），而使用雄性可育样本（MF）序列进行了 mtDNA 草案组装（166,124 个核苷酸，94 个连续）。从它们的注释和比对中，鉴定出了两个类似的序列。在 CMS 样本的 mtDNA 中仅发现了具有 5'端 300bp 截断的假定突变拷贝，而野生型拷贝（）仅在 MF mtDNA 中检测到。进一步的分析（即读数映射和 Sanger 测序）表明，在 CMS 样本中也存在 拷贝，可能在核 DNA 中。然而，在不同组织上进行的 qPCR 证明，尽管其存在，仅在 MF 样本中表达 ，而在 CMS 个体中始终检测到 mRNA。根据这些发现，能量缺乏模型可以解释雄性不育花中花粉缺乏的现象。 可能代表一个基因，其 mRNA 翻译成不完全功能的蛋白质，导致 ATP 产生不足，足以保证基本的细胞过程，但不足以满足花粉发育等高能量需求过程。我们的研究为茴香 mtDNA 基因组及其 基因提供了新的见解，并为进一步研究其在雄性不育决定中的功能作用铺平了道路。
