Yao Youming, Zhang Hongyu, Guo Rong, Fan Jiangmin, Liu Siyi, Liao Jianglin, Huang Yingjin, Wang Zhaohai
Key Laboratory of Crop Physiology, Ecology and Genetic Breeding (Jiangxi Agricultural University), Ministry of Education of the P.R. China, Nanchang 330045, China.
Key Laboratory of Agriculture Responding to Climate Change (Jiangxi Agricultural University), Nanchang 330045, China.
Plants (Basel). 2023 Nov 6;12(21):3785. doi: 10.3390/plants12213785.
Functional defects in key genes for chlorophyll synthesis usually cause abnormal chloroplast development, but the genetic regulatory network for these key genes in regulating chloroplast development is still unclear. Magnesium protoporphyrin IX methyltransferase (ChlM) is a key rate-limiting enzyme in the process of chlorophyll synthesis. Physiological analysis showed that the chlorophyll and carotenoid contents were significantly decreased in the mutant. Transmission electron microscopy demonstrated that the chloroplasts of the mutant were not well developed, with poor, loose, and indistinct thylakoid membranes. Hormone content analysis found that jasmonic acid, salicylic acid, and auxin accumulated in the mutant. A comparative transcriptome profiling identified 1534 differentially expressed genes (DEGs) between and the wild type, including 876 up-regulated genes and 658 down-regulated genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that these DEGs were highly involved in chlorophyll metabolism, chloroplast development, and photosynthesis. Protein-protein interaction network analysis found that protein translation played an essential role in the gene-regulated process. Specifically, 62 and 6 DEGs were annotated to regulate chlorophyll and carotenoid metabolism, respectively; 278 DEGs were predicted to be involved in regulating chloroplast development; 59 DEGs were found to regulate hormone regulatory pathways; 192 DEGs were annotated to regulate signal pathways; and 49 DEGs were putatively identified as transcription factors. Dozens of these genes have been well studied and reported to play essential roles in chlorophyll accumulation or chloroplast development, providing direct evidence for the reliability of the role of the identified DEGs. These findings suggest that chlorophyll synthesis and chloroplast development are actively regulated by the gene. And it is suggested that hormones, signal pathways, and transcription regulation were all involved in these regulation processes. The accuracy of transcriptome data was validated by quantitative real-time PCR (qRT-PCR) analysis. This study reveals a complex genetic regulatory network of the gene regulating chlorophyll synthesis and chloroplast development. The gene's role in retrograde signaling was discussed. Jasmonic acid, salicylic acid, or their derivatives in a certain unknown state were proposed as retrograde signaling molecules in one of the signaling pathways from the chloroplast to nucleus.
叶绿素合成关键基因的功能缺陷通常会导致叶绿体发育异常，但这些关键基因调控叶绿体发育的遗传调控网络仍不清楚。镁原卟啉IX甲基转移酶（ChlM）是叶绿素合成过程中的关键限速酶。生理分析表明，突变体中的叶绿素和类胡萝卜素含量显著降低。透射电子显微镜显示，突变体的叶绿体发育不良，类囊体膜结构差、松散且不清晰。激素含量分析发现，茉莉酸、水杨酸和生长素在突变体中积累。比较转录组分析确定了突变体与野生型之间有1534个差异表达基因（DEG），其中包括876个上调基因和658个下调基因。基因本体论（GO）和京都基因与基因组百科全书（KEGG）分析表明，这些DEG高度参与叶绿素代谢、叶绿体发育和光合作用。蛋白质-蛋白质相互作用网络分析发现，蛋白质翻译在ChlM基因调控过程中起重要作用。具体而言，分别有62个和6个DEG被注释为调控叶绿素和类胡萝卜素代谢；278个DEG预计参与调控叶绿体发育；59个DEG被发现调控激素调节途径；192个DEG被注释为调控信号通路；49个DEG被推定鉴定为转录因子。其中许多基因已经得到充分研究，并报道在叶绿素积累或叶绿体发育中起重要作用，为所鉴定的DEG作用的可靠性提供了直接证据。这些发现表明，ChlM基因积极调控叶绿素合成和叶绿体发育。并且表明激素、信号通路和转录调控都参与了这些调控过程。通过定量实时PCR（qRT-PCR）分析验证了转录组数据的准确性。本研究揭示了ChlM基因调控叶绿素合成和叶绿体发育的复杂遗传调控网络。讨论了ChlM基因在逆行信号传导中的作用。提出茉莉酸、水杨酸或其某种未知状态的衍生物作为从叶绿体到细胞核的一条信号通路中的逆行信号分子。
