College of Agronomy, Northwest A & F University, Key Laboratory of Crop Heterosis of Shaanxi Province, Wheat Breeding Engineering Research Center, Ministry of Education, Yangling, 712100, Shaanxi, China.
School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, 200240, China.
BMC Plant Biol. 2023 Dec 6;23(1):618. doi: 10.1186/s12870-023-04611-2.
Cytoplasmic male sterility (CMS) plays a crucial role in hybrid production. K-type CMS, a cytoplasmic male sterile line of wheat with the cytoplasms of Aegilops kotschyi, is widely used due to its excellent characteristics of agronomic performance, easy maintenance and easy restoration. However, the mechanism of its pollen abortion is not yet clear.
In this study, wheat K-type CMS MS(KOTS)-90-110 (MS line) and it's fertile near-isogenic line MR (KOTS)-90-110 (MR line) were investigated. Cytological analysis indicated that the anthers of MS line microspore nucleus failed to divide normally into two sperm nucleus and lacked starch in mature pollen grains, and the key abortive period was the uninucleate stage to dinuclear stage. Then, we compared the transcriptome of MS line and MR line anthers at these two stages. 11,360 and 5182 differentially expressed genes (DEGs) were identified between the MS and MR lines in the early uninucleate and binucleate stages, respectively. Based on GO enrichment and KEGG pathways analysis, it was evident that significant transcriptomic differences were "plant hormone signal transduction", "MAPK signaling pathway" and "spliceosome". We identified 17 and 10 DEGs associated with the IAA and ABA signal transduction pathways, respectively. DEGs related to IAA signal transduction pathway were downregulated in the early uninucleate stage of MS line. The expression level of DEGs related to ABA pathway was significantly upregulated in MS line at the binucleate stage compared to MR line. The determination of plant hormone content and qRT-PCR further confirmed that hormone imbalance in MS lines. Meanwhile, 1 and 2 DEGs involved in ABA and Ethylene metabolism were also identified in the MAPK cascade pathway, respectively; the significant up regulation of spliceosome related genes in MS line may be another important factor leading to pollen abortion.
We proposed a transcriptome-mediated pollen abortion network for K-type CMS in wheat. The main idea is hormone imbalance may be the primary factor, MAPK cascade pathway and alternative splicing (AS) may also play important regulatory roles in this process. These findings provided intriguing insights for the molecular mechanism of microspore abortion in K-type CMS, and also give useful clues to identify the crucial genes of CMS in wheat.
细胞质雄性不育（CMS）在杂种生产中起着至关重要的作用。K 型 CMS 是一种小麦细胞质雄性不育系，其细胞质来源于节节麦，具有良好的农艺性状、易于保持和易于恢复等特点，因此被广泛应用。然而，其花粉败育的机制尚不清楚。
本研究以小麦 K 型 CMS 材料 MS（KOTS）-90-110（不育系）及其可育近等基因系 MR（KOTS）-90-110（保持系）为材料，细胞学观察发现不育系小孢子核在成熟花粉粒中无法正常分裂为两个精核，且缺乏淀粉，其败育关键时期是单核期到双核期。然后，我们比较了这两个时期 MS 系和 MR 系花药的转录组。在早期单核期和双核期，MS 系和 MR 系之间分别鉴定出 11360 个和 5182 个差异表达基因（DEGs）。基于 GO 富集和 KEGG 途径分析，明显的转录组差异存在于“植物激素信号转导”、“MAPK 信号通路”和“剪接体”。我们分别鉴定出 17 个和 10 个与 IAA 和 ABA 信号转导途径相关的 DEGs。在 MS 系早期单核期，与 IAA 信号转导途径相关的 DEGs 下调。与 MR 系相比，MS 系在双核期 ABA 途径相关 DEGs 的表达水平显著上调。激素含量的测定和 qRT-PCR 进一步证实了 MS 系中激素失衡的情况。同时，在 MAPK 级联途径中还分别鉴定出 1 个和 2 个与 ABA 和乙烯代谢相关的 DEGs；MS 系中剪接体相关基因的显著上调可能是导致花粉败育的另一个重要因素。
我们提出了一个小麦 K 型 CMS 花粉败育的转录组调控网络。主要观点是激素失衡可能是主要因素，MAPK 级联途径和可变剪接（AS）也可能在这个过程中发挥重要的调控作用。这些发现为 K 型 CMS 花粉败育的分子机制提供了有趣的见解，也为鉴定小麦 CMS 的关键基因提供了有用的线索。
