ITRAQ-based quantitative proteomic analysis of japonica rice seedling during cold stress

Proteomes and ubiquitylomes reveal the regulation mechanism of cold tolerance mediated by OsGRF4 in rice

Low temperature is one of the major abiotic stresses that severely restrict the development of rice. It has been demonstrated previously that OsGRF4 enhances cold tolerance in rice, the molecular mechanism of which remains unknown. This study employed a combination of proteome and ubiquitylome approaches to analyze OsGRF4 mediated chilling between the overexpression line (OX) and wild type (CK). Proteome results showed that 6,157 proteins were identified and 5,045 proteins were quantified after 24-h cold treatment. A total of 59 proteins were upregulated and 63 proteins were downregulated in the OX24 vs. OX0 group; 27 proteins were upregulated and 34 proteins were downregulated in OX24 vs. CK24. Finally, 3,789 ubiquitination modification sites were located on 1,846 proteins, of which 2,695 sites of 1,376 proteins contained quantitative information. However, 178 sites in 131 proteins were quantified as upregulated and 92 sites in 72 proteins were quantified as downregulated differentially ubiquitin-modified proteins (DUMPs) in OX24 vs. OX0. To the contrary, 82 sites in 71 proteins were identified as upregulated and 13 sites in 12 proteins were identified as downregulated DUMPs in CK24 vs. OX24. The results suggested that global ubiquitination levels increase during cold tolerance in rice. In total, 76 differentially abundant proteins and 101 DUMPs were co-localized within 50 cold or stress tolerance Quantitative Trait Locis (QTLs). The combined analysis of proteomics and ubiquitination omics found that five proteins demonstrated opposing changes in protein and ubiquitination; the protein Q6ZH84 (Os02g0593700) was an upregulated differentially abundant protein (DAP) but was a downregulated DUMP in OX24 vs. OX0, which is a homologous gene of NBR1 that regulated cold tolerance. Os02g0593700 should upregulate protein expression by reducing ubiquitination modification, thus affecting cold tolerance. The enrichment pathway shows that OsGRF4 plays an important role in rice cold tolerance by ubiquitination through glutathione metabolism and arachidonic acid metabolism. The research provides a new perspective on the molecular mechanism of cold tolerance regulated by OsGRF4.

iTRAQ-based quantitative proteomic analysis of herbicide stress in Avena ludoviciana Durieu

Winter wild oat (Avena sterilis subsp. ludoviciana (Durieu) Gillet & Magne) has been considered the most common and troublesome weed in wheat fields of Iran. The widespread and continuous use of herbicides has led to the emergence and development of resistant biotypes in A. ludoviciana, making it one of the most important herbicide-resistant weeds within field crops. Considering the importance of understanding the mechanisms underlying resistance to herbicides and identifying key proteins involved in the response to Acetyl-coenzyme A carboxylase (ACCase) and Acetolactate synthase (ALS) inhibitor herbicides in A. ludoviciana. This study aimed to identify the proteins involved in herbicide resistance in A. ludoviciana using the Isobaric Tags for Relative and Absolute Quantification (iTRAQ) technique. In this study, a total of 18,313 peptides were identified with ≤ 0.01 FDR, which could be classified into 484 protein groups. Additionally, 138 differentially expressed proteins (DEPs) were identified in the resistant biotype (R), while 93 DEPs were identified in the susceptible biotype (S). Gene Ontology (GO) analysis revealed that these DEPs mainly consisted of proteins related to photosynthesis, respiration, amino acid synthesis and translation, secondary metabolite biosynthesis, defense proteins, and detoxification. Furthermore, enrichment pathway analysis using Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that the most important pathways included metabolic pathways, carbohydrate metabolism, secondary metabolites, amino acid synthesis, and photosynthesis. The function of DEPs indicated that some proteins, such as cytochrome P450, play a direct role in herbicide detoxification. Overall, the results of this study demonstrated the complex response of the resistant biotype to herbicides and its ability to increase antioxidant capacity through up-regulated detoxification proteins, particularly cytochrome P450 (Q6YSB4), and defense proteins, particularly superoxide dismutase (Q0DRV6) and polyamine oxidase (Q7XR46). In the resistant A. ludoviciana populations, in addition to the activation of enzymatic and non-enzymatic defense systems, other strategies such as reduced photosynthesis and respiration, increased transcription and translation activity, enhanced lipid metabolism, regulation of cellular processes and homeostasis, and up-regulation of proteins associated with signaling and ion channels play a role in resistance to herbicide. Overall these findings provide new insights into the role of different proteins in resistance to herbicides and contribute to a comprehensive understanding of herbicide resistance in A. ludoviciana.

Integrated Review of Transcriptomic and Proteomic Studies to Understand Molecular Mechanisms of Rice's Response to Environmental Stresses

Rice (Oryza sativa L.) is grown nearly worldwide and is a staple food for more than half of the world's population. With the rise in extreme weather and climate events, there is an urgent need to decode the complex mechanisms of rice's response to environmental stress and to breed high-yield, high-quality and stress-resistant varieties. Over the past few decades, significant advancements in molecular biology have led to the widespread use of several omics methodologies to study all aspects of plant growth, development and environmental adaptation. Transcriptomics and proteomics have become the most popular techniques used to investigate plants' stress-responsive mechanisms despite the complexity of the underlying molecular landscapes. This review offers a comprehensive and current summary of how transcriptomics and proteomics together reveal the molecular details of rice's response to environmental stresses. It also provides a catalog of the current applications of omics in comprehending this imperative crop in relation to stress tolerance improvement and breeding. The evaluation of recent advances in CRISPR/Cas-based genome editing and the application of synthetic biology technologies highlights the possibility of expediting the development of rice cultivars that are resistant to stress and suited to various agroecological environments.

Editing of rice (Oryza sativa L.) OsMKK3 gene using CRISPR/Cas9 decreases grain length by modulating the expression of photosystem components

Grain size is one of the most important agronomic traits for grain yield determination in rice. To better understand the proteins that are regulated by the grain size regulatory gene OsMKK3, this gene was knocked out using the CRISPR/Cas9 system, and tandem mass tag (TMT) labeling combined with liquid chromatograph-tandem mass spectrometry analysis was performed to study the regulation of proteins in the panicle. Quantitative proteomic screening revealed a total of 106 differentially expressed proteins (DEPs) via comparison of the OsMKK3 mutant line to the wild-type YexiangB, including 15 and 91 up-regulated and down-regulated DEPs, respectively. Pathway analysis revealed that DEPs were enriched in metabolic pathways, biosynthesis of secondary metabolites, phenylpropanoid biosynthesis, and photosynthesis. Strong interactions were detected among seven down-regulated proteins related to photosystem components in the protein-protein interaction network, and photosynthetic rate was decreased in mutant plants. The results of the liquid chromatography-parallel reaction monitoring/mass spectromery analysis and western blot analysis were consistent with the results of the proteomic analysis, and the results of the quantitative reverse transcription polymerase chain reaction analysis revealed that the expression levels of most candidate genes were consistent with protein levels. Overall, OsMKK3 controls grain size by regulating the protein content in cells. Our findings provide new candidate genes that will aid the study of grain size regulatory mechanisms associated with the mitogen-activated protein kinase (MAPK) signaling pathway.

TMT-based quantitative proteomic analysis of indica rice cultivars reveals that novel components of the signaling pathways might play a role in grain length regulation

Grain length is one of the most important rice grain appearance components. To better understand the protein regulated by grain length in indica rice, the tandem mass tag (TMT) labeling combined with LC-MS/MS analysis was used for quantitative identification of differentially regulated proteins by comparing six long-grain cultivars (MeiB, LongfengB, YexiangB, FengtianB, WantaiB, and DingxiangB) to the short-grain cultivar BoB, respectively. A total of 6622 proteins were detected for quantitative analysis by comparing protein content of six long-grain cultivars to the short-grain cultivar, and 715 proteins were significantly regulated, consisting of 336 uniquely over-accumulated proteins and 355 uniquely down-accumulated proteins. KEGG pathway analysis revealed that most of accumulated proteins are involved in metabolic pathways, biosynthesis of secondary metabolites and phenylpropanoid biosynthesis. Four down-accumulated proteins maybe involved in the signaling pathways for grain length regulation. LC-PRM/MS quantitative analysis was used to analyze 10 differentially expressed proteins. The results were almost consistent with the TMT quantitative analysis. qRT-PCR analysis results showed that the transcription level was not always parallel to the protein content. This study identified many novel grain length accumulated proteins through the quantitative proteomics approach, providing candidate genes for further study of grain size regulatory mechanisms. SIGNIFICANCE: Rice grain length is one of the most important characteristics influencing appearance and yield. Six long-grain cultivars (MeiB, LongfengB, YexiangB, FengtianB, WantaiB, and DingxiangB obtained in Guangxi province of China from the 2000s to 2020s) and one short-grain cultivar (BoB obtained in Guangxi province of China in 1980s) were used for comparative analyses. Totally, 715 differentially expressed proteins (DEPs) were identified using TMT-base proteomic analysis. The numbers of DEPs increased as the grain length increased. 4 DEPs may be related to rice's signaling pathways for grain size regulation. A total of 85 DEPs regulated in at least four long-grain cultivars compared with the short-grain cultivar BoB, and 7 proteins were over-accumulated, and 3 proteins were down-accumulated in six long-grain cultivars. These findings provide valuable information to better understand the mechanisms of protein regulation by grain length in rice.