TMT-based quantitative proteomics analyses of sterile/fertile anthers from a genic male-sterile line and its maintainer in cotton (Gossypium hirsutum L.)

Anatomy and Comparative Transcriptome Reveal the Mechanism of Male Sterility in Salvia miltiorrhiza

Salvia miltiorrhiza Bunge is an important traditional herb. Salvia miltiorrhiza is distributed in the Sichuan province of China (here called SC). Under natural conditions, it does not bear seeds and its sterility mechanism is still unclear. Through artificial cross, there was defective pistil and partial pollen abortion in these plants. Electron microscopy results showed that the defective pollen wall was caused by delayed degradation of the tapetum. Due to the lack of starch and organelle, the abortive pollen grains showed shrinkage. RNA-seq was performed to explore the molecular mechanisms of pollen abortion. KEGG enrichment analysis suggested that the pathways of phytohormone, starch, lipid, pectin, and phenylpropanoid affected the fertility of S. miltiorrhiza. Moreover, some differentially expressed genes involved in starch synthesis and plant hormone signaling were identified. These results contribute to the molecular mechanism of pollen sterility and provide a more theoretical foundation for molecular-assisted breeding.

Integrative analysis of metabolome and transcriptome reveals the improvements of seed quality in vegetable soybean (Glycine max (L.) Merr.)

Vegetable soybean is derived from grain soybean. Seeds of vegetable soybean are bigger, sweeter, and have smoother texture and better flavor than those of grain soybean. To better understand the improvements of seed quality in vegetable soybean, comparative metabolome and transcriptome analyses were performed in the developing seeds between grain (Williams 82) and vegetable (Jiaoda 133) soybeans. A total of 299 differential metabolites were identified between two genotypes, with an increase in free amino acids, carbohydrates, sterols, and flavonoids and a decrease in fatty acid in vegetable soybean. Thousands of differentially expressed genes (DEGs) were identified by transcriptome analysis. DEGs were used for weighted gene co-expression network analysis (WGCNA), yielding 16 co-expression modules. The expression patterns of DEGs within these modules were distinct between two genotypes. Functional enrichment analysis revealed that metabolic pathways, including alanine, aspartate and glutamate metabolism, fatty acid degradation, starch and sucrose metabolism, sucrose transport, and flavonoid biosynthesis, were up-regulated, whereas photosynthesis, arginine biosynthesis, arginine and proline metabolism, glycolysis/gluconeogenesis, and fatty acid biosynthesis were down-regulated in vegetable soybean. Reasonably, the alterations of metabolic pathways corresponding to DEGs partly explained the formation of differential metabolites. These findings provide a better understanding of seed development and breeding improvements of vegetable soybean.

The proteome of developing barley anthers during meiotic prophase I

Flowering plants reproduce sexually by combining a haploid male and female gametophyte during fertilization. Male gametophytes are localized in the anthers, each containing reproductive (meiocyte) and non-reproductive tissue necessary for anther development and maturation. Meiosis, where chromosomes pair and exchange their genetic material during a process called recombination, is one of the most important and sensitive stages in breeding, ensuring genetic diversity. Most anther development studies have focused on transcript variation, but very few have been correlated with protein abundance. Taking advantage of a recently published barley anther transcriptomic (BAnTr) dataset and a newly developed sensitive mass spectrometry-based approach to analyse the barley anther proteome, we conducted high-resolution mass spectrometry analysis of barley anthers, collected at six time points and representing their development from pre-meiosis to metaphase. Each time point was carefully staged using immunocytology, providing a robust and accurate staging mirroring our previous BAnTr dataset. We identified >6100 non-redundant proteins including 82 known and putative meiotic proteins. Although the protein abundance was relatively stable throughout prophase I, we were able to quantify the dynamic variation of 336 proteins. We present the first quantitative comparative proteomics study of barley anther development during meiotic prophase I when the important process of homologous recombination is taking place.

TMT-based comparative proteomic analysis of the male-sterile mutant ms01 sheds light on sporopollenin production and pollen development in wucai (Brassica campestris L.)

A spontaneous male-sterile mutant ms01 was discovered from the excellent high-generation inbred line 'hx12-6-3' in wucai. Compared with wild-type 'hx12-6-3', ms01 displayed complete male sterility with degenerated stamens and no pollen. In this study, cytological observation revealed that the tapetum of the anthers of ms01 had degraded in advance, and microspore development had stagnated in the mononuclear stage, ultimately resulting in completely aborted pollen. Genetic analysis indicated that the sterility of ms01 was controlled by a single recessive nuclear gene. In the differential proteomic analysis of 'hx12-6-3' and ms01 flower buds using a tandem mass tags-based approach, a comparison of two stages (stage a and stage e) revealed 1272 differentially abundant proteins (DAPs). The abnormal variation of the anther cuticle, pollen coat, and sporopollenin production were effected by lipid metabolism and phenylpropanoid biosynthesis in the mutant ms01. Further analysis elucidated that pollen development was associated with amino acid metabolism, protein synthesis and degradation, carbohydrate metabolism, flavonoid biosynthesis and glutathione metabolism. These results provide novel insights into the molecular mechanism of GMS (genic male sterility) in wucai. SIGNIFICANCE: ms01, as the first indentified spontaneous male-sterile mutant in wucai, plays a significant role in the initial study of GMS (genic male sterility). In our study, the key DAPs related to anther and pollen development were obtained by TMT-based comparative proteomic analysis. We found that the abnormal accumulation of H₂O₂ might induce premature degradation of the tapetum, causing anther metabolism disorder and pollen abortion. This process involved multiple DAPs and formed a complex regulatory network that generated a series of physiological metabolic alterations, ultimately leading to male sterility. Our results provide a theoretical foundation for further research on the complex anther and pollen development process.

Rational Proteomic Analysis of a New Domesticated Klebsiella pneumoniae x546 Producing 1,3-Propanediol

In order to improve the capability of Klebsiella pneumoniae to produce an important chemical raw material, 1,3-propanediol (1,3-PDO), a new type of K. pneumoniae x546 was obtained by glycerol acclimation and subsequently was used to produce 1,3-PDO. Under the control of pH value using Na⁺ pH neutralizer, the 1,3-PDO yield of K. pneumoniae x546 in a 7.5-L fermenter was 69.35 g/L, which was 1.5-fold higher than the original strain (45.91 g/L). After the addition of betaine, the yield of 1,3-PDO reached up to 74.44 g/L at 24 h, which was 40% shorter than the original fermentation time of 40 h. To study the potential mechanism of the production improvement of 1,3-PDO, the Tandem Mass Tags (TMT) technology was applied to investigate the production of 1,3-PDO in K. pneumoniae. Compared with the control group, 170 up-regulated proteins and 291 down-regulated proteins were identified. Through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis, it was found that some proteins [such as homoserine kinase (ThrB), phosphoribosylglycinamide formyltransferase (PurT), phosphoribosylaminoimidazolesuccinocarboxamide synthase (PurC), etc.] were involved in the fermentation process, whereas some other proteins (such as ProX, ProW, ProV, etc.) played a significant role after the addition of betaine. Moreover, combined with the metabolic network of K. pneumoniae during 1,3-PDO, the proteins in the biosynthesis of 1,3-PDO [such as DhaD, DhaK, lactate dehydrogenase (LDH), BudC, etc.] were analyzed. The process of 1,3-PDO production in K. pneumoniae was explained from the perspective of proteome for the first time, which provided a theoretical basis for genetic engineering modification to improve the yield of 1,3-PDO. Because of the use of Na⁺ pH neutralizer in the fermentation, the subsequent environmental pollution treatment cost was greatly reduced, showing high potential for industry application in the future.

Effects of Simulated Microgravity on the Physiology of Stenotrophomonas maltophilia and Multiomic Analysis

Many studies have shown that the space environment plays a pivotal role in changing the characteristics of conditional pathogens, especially their pathogenicity and virulence. However, Stenotrophomonas maltophilia, a type of conditional pathogen that has shown to a gradual increase in clinical morbidity in recent years, has rarely been reported for its impact in space. In this study, S. maltophilia was exposed to a simulated microgravity (SMG) environment in high-aspect ratio rotating-wall vessel bioreactors for 14days, while the control group was exposed to the same bioreactors in a normal gravity (NG) environment. Then, combined phenotypic, genomic, transcriptomic, and proteomic analyses were conducted to compare the influence of the SMG and NG on S. maltophilia. The results showed that S. maltophilia in simulated microgravity displayed an increased growth rate, enhanced biofilm formation ability, increased swimming motility, and metabolic alterations compared with those of S. maltophilia in normal gravity and the original strain of S. maltophilia. Clusters of Orthologous Groups (COG) annotation analysis indicated that the increased growth rate might be related to the upregulation of differentially expressed genes (DEGs) involved in energy metabolism and conversion, secondary metabolite biosynthesis, transport and catabolism, intracellular trafficking, secretion, and vesicular transport. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that the increased motility might be associated the upregulation of differentially expressed proteins (DEPs) involved in locomotion, localization, biological adhesion, and binding, in accordance with the upregulated DEGs in cell motility according to COG classification, including pilP, pilM, flgE, flgG, and ronN. Additionally, the increased biofilm formation ability might be associated with the upregulation of DEPs involved in biofilm formation, the bacterial secretion system, biological adhesion, and cell adhesion, which were shown to be regulated by the differentially expressed genes (chpB, chpC, rpoN, pilA, pilG, pilH, and pilJ) through the integration of transcriptomic and proteomic analyses. These results suggested that simulated microgravity might increase the level of corresponding functional proteins by upregulating related genes to alter physiological characteristics and modulate growth rate, motility, biofilm formation, and metabolism. In conclusion, this study is the first general analysis of the phenotypic, genomic, transcriptomic, and proteomic changes in S. maltophilia under simulated microgravity and provides some suggestions for future studies of space microbiology.

Morphological characteristics and transcriptome analysis at different anther development stages of the male sterile mutant MS7-2 in Wucai (Brassica campestris L.)

BACKGROUND

The discovery of male sterile materials is of great significance for the development of plant fertility research. Wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen) is a variety of non-heading Chinese cabbage. There are few studies on the male sterility of wucai, and the mechanism of male sterility is not clear. In this study, the male sterile mutant MS7-2 and the wild-type fertile plant MF7-2 were studied.

RESULTS

Phenotypic characteristics and cytological analysis showed that MS7-2 abortion occurred at the tetrad period. The content of related sugars in the flower buds of MS7-2 was significantly lower than that of MF7-2, and a large amount of reactive oxygen species (ROS) was accumulated. Through transcriptome sequencing of MS7-2 and MF7-2 flower buds at three different developmental stages (a-c), 2865, 3847, and 4981 differentially expressed genes were identified in MS7-2 at the flower bud development stage, stage c, and stage e, respectively, compared with MF7-2. Many of these genes were enriched in carbohydrate metabolism, phenylpropanoid metabolism, and oxidative phosphorylation, and most of them were down-regulated in MS7-2. The down-regulation of genes involved in carbohydrate and secondary metabolite synthesis as well as the accumulation of ROS in MS7-2 led to pollen abortion in MS7-2.

CONCLUSIONS

This study helps elucidate the mechanism of anther abortion in wucai, providing a basis for further research on the molecular regulatory mechanisms of male sterility and the screening and cloning of key genes in wucai.

Phosphoproteomic Analysis of Thermomorphogenic Responses in Arabidopsis

Plants rapidly adapt to elevated ambient temperature by adjusting their growth and developmental programs. To date, a number of experiments have been carried out to understand how plants sense and respond to warm temperatures. However, how warm temperature signals are relayed from thermosensors to transcriptional regulators is largely unknown. To identify new early regulators of plant thermo-responsiveness, we performed phosphoproteomic analysis using TMT (Tandem Mass Tags) labeling and phosphopeptide enrichment with Arabidopsis etiolated seedlings treated with or without 3h of warm temperatures (29°C). In total, we identified 13,160 phosphopeptides in 5,125 proteins with 10,700 quantifiable phosphorylation sites. Among them, 200 sites (180 proteins) were upregulated, while 120 sites (87 proteins) were downregulated by elevated temperature. GO (Gene Ontology) analysis indicated that phosphorelay-related molecular function was enriched among the differentially phosphorylated proteins. We selected ATL6 (ARABIDOPSIS TOXICOS EN LEVADURA 6) from them and expressed its native and phosphorylation-site mutated (S343A S357A) forms in Arabidopsis and found that the mutated form of ATL6 was less stable than that of the native form both in vivo and in cell-free degradation assays. Taken together, our data revealed extensive protein phosphorylation during thermo-responsiveness, providing new candidate proteins/genes for studying plant thermomorphogenesis in the future.