Diversity and enzymatic potentialities of <Emphasis Type="Italic">Bacillus</Emphasis> sp. strains isolated from a polluted freshwater ecosystem in Cuba

Genotypic and phenotypic characterization of Bacillus spp. from polluted freshwater has been poorly addressed. The objective of this research was to determine the diversity and enzymatic potentialities of Bacillus spp. strains isolated from the Almendares River. Bacilli strains from a polluted river were characterized by considering the production of extracellular enzymes using API ZYM. 14 strains were selected and identified using 16S rRNA, gyrB and aroE genes. Genotypic diversity of the Bacillus spp. strains was evaluated using pulsed field gel electrophoresis. Furthermore, the presence of genetic determinants of potential virulence toxins of the Bacillus cereus group and proteinaceous crystal inclusions of Bacillus thuringiensis was determined. 10 strains were identified as B. thuringiensis, two as Bacillus megaterium, one as Bacillus pumilus and one as Bacillus subtilis. Most strains produced proteases, amylases, phosphatases, esterases, aminopeptidases and glucanases, which reflect the abundance of biopolymeric matter in Almendares River. Comparison of the typing results revealed a spatio-temporal distribution among B. thuringiensis strains along the river. The results of the present study highlight the genotypic and phenotypic diversity of Bacillus spp. strains from a polluted river, which contributes to the knowledge of genetic diversity of Bacilli from tropical polluted freshwater ecosystems.     

Identification of <Emphasis Type="Italic">Bacillus</Emphasis> Probiotics Isolated from Soil Rhizosphere Using 16S rRNA, <Emphasis Type="Italic">recA</Emphasis>, <Emphasis Type="Italic">rpoB</Emphasis> Gene Sequencing and RAPD-PCR

Some Bacillus species, especially Bacillus subtilis and Bacillus pumilus groups, have highly similar 16S rRNA gene sequences, which are hard to identify based on 16S rDNA sequence analysis. To conquer this drawback, rpoB, recA sequence analysis along with randomly amplified polymorphic (RAPD) fingerprinting was examined as an alternative method for differentiating Bacillus species. The 16S rRNA, rpoB and recA genes were amplified via a polymerase chain reaction using their specific primers. The resulted PCR amplicons were sequenced, and phylogenetic analysis was employed by MEGA 6 software. Identification based on 16S rRNA gene sequencing was underpinned by rpoB and recA gene sequencing as well as RAPD-PCR technique. Subsequently, concatenation and phylogenetic analysis showed that extent of diversity and similarity were better obtained by rpoB and recA primers, which are also reinforced by RAPD-PCR methods. However, in one case, these approaches failed to identify one isolate, which in combination with the phenotypical method offsets this issue. Overall, RAPD fingerprinting, rpoB and recA along with concatenated genes sequence analysis discriminated closely related Bacillus species, which highlights the significance of the multigenic method in more precisely distinguishing Bacillus strains. This research emphasizes the benefit of RAPD fingerprinting, rpoB and recA sequence analysis superior to 16S rRNA gene sequence analysis for suitable and effective identification of Bacillus species as recommended for probiotic products.     

Evaluation of the Diversity of Probiotic <Emphasis Type="Italic">Bacillus</Emphasis>, <Emphasis Type="Italic">Clostridium</Emphasis>, and <Emphasis Type="Italic">Bifidobacterium</Emphasis> Using the Illumina-Based Sequencing Method

Bacterial species of Bacillus, Lactobacillus, and Bifidobacterium in the intestinal tract have been used as probiotics. Selections for probiotic candidates by the culture-based approaches are time-consuming and labor-consuming. The aim of this study was to develop a new method based on sequencing strategies to select the probiotic Bacillus, Lactobacillus, and Bifidobacterium. The Illumina-based sequencing strategies with different specific primers for Bacillus, Clostridium, and Bifidobacterium were applied to analyze diversity of the genera in goat feces. The average number of different Bacillus, Clostridium, and Bifidobacterium OTUs (operational taxonomic units) at the 97% similarity level ranged from 1922 to 63172. The coverage index values of Bacillus, Clostridium, and Bifidobacterium calculated from the bacterial OTUs were 0.89, 0.99, and 1.00, respectively. The most genera of Bacillus (37.9%), Clostridium (53%), and Bifidobacterium (99%) were detected in goat feces by the Illumina-based sequencing with the specific primers of the genera, respectively. Higher phylogenetic resolutions of the genera in goat feces were successfully established. The results suggest that the selection for probiotic Bacillus, Clostridium, and Bifidobacterium based on the Illumina sequencing with their specific primers is reliable and feasible, and the core Bacillus, Clostridium, and Bifidobacterium species of healthy goats possess the potentials as probiotic microbial consortia.     

Strains of <Emphasis Type="Italic">Bacillus</Emphasis> ssp. regulate wheat resistance to <Emphasis Type="Italic">Septoria nodorum</Emphasis> Berk.

The ability of Bacillus subtilis Cohn and Bacillus thuringiensis Berliner to induce systemic resistance in wheat plants to the casual agent of Septoria nodorum Berk., blotch has been studied. It has been shown that strains of Bacillus ssp. that possess the capacity for endophytic survival have antagonistic activity against this pathogen in vitro. A reduction of the degree of Septoria nodorum blotch development on wheat leaves under the influence of Bacillus spp. was accompanied by the suppression of catalase activity, an increase in peroxidase activity and H₂O₂ content, and expression of defence related genes such us PR-1, PR-6, and PR-9. It has been shown that B. subtilis 26 D induces expression levels of wheat pathogenesis-related (PR) genes which marks a SA-dependent pathway of sustainable development and that B. thuringiensis V-5689 and V-6066 induces a JA/ET-dependent pathway. These results suggest that these strain Bacillus spp. promotes the formation of wheat plant resistance to S. nodorum through systemic activation of the plant defense system. The designed bacterial consortium formed a complex biological response in wheat plants infected phytopathogen.     

A look into a multifunctional toolbox: endophytic <Emphasis Type="Italic">Bacillus</Emphasis> species provide broad and underexploited benefits for plants

One of the major challenges of agriculture currently is to obtain higher crop yield. Environmental conditions, cultivar quality, and plant diseases greatly affect plant productivity. On the other hand, several endophytic Bacillus species have emerged as a complementary, efficient, and safe alternative to current crop management practices. The ability of Bacillus species to form spores, which resist adverse conditions, is an advantage of the genus for use in formulations. Endophytic Bacillus species provide plants with a wide range of benefits, including protection against phytopathogenic microorganisms, insects, and nematodes, eliciting resistance, and promoting plant growth, without causing damage to the environment. Bacillus thuringiensis, B. subtilis, B. amyloliquefaciens, B. velezensis, B. cereus, B. pumilus, and B. licheniformis are the most studied Bacillus species for application in agriculture, although other species within the genus have also shown great potential. Due to the increasing number of whole-genome sequenced endophytic Bacillus spp. strains, various bioactive compounds have been predicted. These data reveal endophytic Bacillus species as an underexploited source of novel molecules of biotechnological interest. In this review, we discuss how endophytic Bacillus species are a valuable multifunctional toolbox to be integrated with crop management practices for achieving higher crop yield.     

Sequence Analysis and Comparative Bioinformatics Study of Camelysin Gene (<Emphasis Type="Italic">calY</Emphasis>) Isolated from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis>

Bacillus strains have been widely used for the production of fibrinolytic enzymes having role in the treatment of cardiovascular disorders. Purification and overproduction of such enzymes has increased their usage in medical fields including metalloproteinases with the ability to degrade extracellular matrix (ECM). Camelysin, a neutral metalloproteinase has been isolated from different species of bacteria like Bacillus cereus, Bacillus anthracis, and Bacillus thuringiensis with fibrinolytic, collagenolytic and actin degradation activity. This project successfully demonstrated the presence of 734-bp coding DNA sequence (CDS) encoding a 20.72331 kDa camelysin gene in local strain of Bacillus thuringiensis containing a signal peptide with cleavage site between residues 19 and 20. The sequence was submitted to GenBank (KT023597) and the sequence showed high homology with the camelysin protein of closely related Bacillus species. The alignment of related proteins through ClustalW displayed difference of four amino acids (“Q” replaced by “P” at position 169 and at position 182–184, “NQE” replaced by “HLK”) in the isolated protein. Comparison including structural and functional analysis of camelysin sequences isolated from different Bacillus species was carried out using different bioinformatics tools and software. The information would help in better understanding the properties of camelysin protein and its role in pathogenicity and clinical treatments.     

<Emphasis Type="Italic">Bacillus spongiae</Emphasis> sp. nov., isolated from sponge of Jeju Island

A Gram-reaction-positive, strictly aerobic, motile, endospore- forming, and rod-shaped bacterial strain designated 135PIL107-10^T was isolated from a sponge on Jeju Island, and its taxonomic position was investigated using a polyphasic approach. Strain 135PIL107-10^T grew at 20–37°C (optimum temperature, 25°C) and pH 6.0–10.0 (optimum pH, 6.0) on marine and R2A agars. Based on 16S rRNA gene phylogeny analysis, the novel strain formed a new branch within the genus Bacillus of the family Bacillaceae, and formed clusters with Bacillus thaohiensis NHI-38^T (96.8%), Bacillus fengqiuensis NPK15^T (96.7%), and Bacillus songklensis CAU 1033^T (96.7%). Lower sequence similarities (97.0%) were found with the type strains of all other recognized members of the genus Bacillus (95.6–96.8% similarity). The G + C content of the genomic DNA was 43.6 mol%. The predominant respiratory quinone was menaquinone-7 and the major fatty acids were iso-C_15:0 and iso-C_17:1ω10c. The overall polar lipid patterns were diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine. The diagnostic diamino acid in the cell-wall peptidoglycan was meso-diaminopimelic acid. The isolate therefore represents a novel species, for which the name Bacillus spongiae sp. nov. is proposed, with the type strain 135PIL107-10^T (= KACC 19275^T = LMG 30080^T).     

Plant growth-promoting potential of endophytic bacteria isolated from roots of wild <Emphasis Type="Italic">Dodonaea viscosa</Emphasis> L.

Dodonaea viscosa, a wild and perennial shrub that can tolerate harsh environmental conditions, was used for the isolation of its endophytic bacteria and their potential was explored for the promotion of Canola growth. The bacteria identified through 16S rRNA gene sequencing, belonged to ten different genera namely Inquilinus, Xanthomonas, Pseudomonas, Rhizobium, Brevundimonas, Microbacterium, Bacillus, Streptomyces, Agrococcus and Stenotrophomonas. All the strains produced small amount of IAA (indole acetic acid) in the absence of tryptophan and comparatively more in the presence of tryptophan. All the bacterial strains were positive for ammonia production, cellulase and pectinase activity, but few of them showed phosphate solubilization, siderophore and hydrogen cyanide production. Only three strains showed ACC (1-aminocyclopropane-1-carboxylate) deaminase activity when tested using in-vitro enzyme assay. Members of genera Bacillus, Pseudomonas and Streptomyces showed positive chitinase, protease and antifungal activity against two phytopathogenic fungi Aspergillus niger and Fusarium oxysoprum, while members of Xanthomonas, Pseudomonas and Bacillus showed significant root elongation of Canola which could be related with their positive plant-growth-promoting (PGP) traits. Among the three plant growth promoting Bacillus strains, B. idriensis is never reported before for its PGP activities. These results showed the potential of Dodonaea viscosa endophytic bacteria as PGPBs, which in future can be further explored for their host range/molecular mechanisms.     

Optimizing the application of <Emphasis Type="Italic">Bacillus velezensis</Emphasis> BAC03 in controlling the disease caused by <Emphasis Type="Italic">Streptomyces scabies</Emphasis>

BAC03 is a novel Bacillus velezensis strain previously studied for biological control of scabby diseases caused by Streptomyces scabies. To optimize its efficacy in disease control, different application strategies of BAC03 were investigated in this study, including timing, frequency, and concentrations of BAC03. BAC03 was either used for seed tuber treatment, foliar application or drenching in potting mix infested with S. scabies. Neither foliar application nor seed treatment affected disease severity. BAC03 applied five days before planting significantly reduced S. scabies population and completely suppressed radish scab, but the later BAC03 was applied the less effective it was. BAC03 at 10⁵ CFU cm^?3 potting mix or higher concentrations was effective in reducing radish scab. Increasing the frequency of BAC03 application did not increase the efficacy on disease reduction. BAC03 also increased the biomass of radish roots and leaves whether the pathogen was present or not.     

Volatile compounds from beneficial or pathogenic bacteria differentially regulate root exudation,transcription of iron transporters,and defense signaling pathways in <Emphasis Type="Italic">Sorghum bicolor</Emphasis>

Key message

Our results show that Sorghum bicolor is able to recognize bacteria through its volatile compounds and differentially respond to beneficial or pathogens via eliciting nutritional or defense adaptive traits.

Abstract

Plants establish beneficial, harmful, or neutral relationships with bacteria. Plant growth promoting rhizobacteria (PGPR) emit volatile compounds (VCs), which may act as molecular cues influencing plant development, nutrition, and/or defense. In this study, we compared the effects of VCs produced by bacteria with different lifestyles, including Arthrobacter agilis UMCV2, Bacillus methylotrophicus M4-96, Sinorhizobium meliloti 1021, the plant pathogen Pseudomonas aeruginosa PAO1, and the commensal rhizobacterium Bacillus sp. L2-64, on S. bicolor. We show that VCs from all tested bacteria, except Bacillus sp. L2-64, increased biomass and chlorophyll content, and improved root architecture, but notheworthy A. agilis induced the release of attractant molecules, whereas P. aeruginosa activated the exudation of growth inhibitory compounds by roots. An analysis of the expression of iron-transporters SbIRT1, SbIRT2, SbYS1, and SbYS2 and genes related to plant defense pathways COI1 and PR-1 indicated that beneficial, pathogenic, and commensal bacteria could up-regulate iron transporters, whereas only beneficial and pathogenic species could induce a defense response. These results show how S. bicolor could recognize bacteria through their volatiles profiles and highlight that PGPR or pathogens can elicit nutritional or defensive traits in plants.

     

Genome analysis reveals insights of the endophytic <Emphasis Type="Italic">Bacillus toyonensis</Emphasis> BAC3151 as a potentially novel agent for biocontrol of plant pathogens

Diseases caused by phytopathogenic microorganisms account for enormous losses for agribusiness. Although Bacillus species are recognized as being antimicrobial producers and some may provide benefits to plants, the association between Bacillus toyonensis and plants has not been studied. In this study, the whole-genome sequenced endophytic B. toyonensis BAC3151, which has demonstrated antimicrobial activity and quorum sensing inhibition of phytopathogenic bacteria, was investigated for its potential for the production of compounds for biocontrol of plant pathogens. Four whole-genome sequenced B. toyonensis strains shared 3811 protein-coding DNA sequences (CDSs), while strain-specific CDSs, such as biosynthetic gene clusters of antimicrobials, were associated with specific chromosomal regions and mobile genetic elements of the strains. B. toyonensis strains had a higher frequency of putative bacteriocins gene clusters than that of Bacillus species traditionally used for the production of antimicrobials. In addition, gene clusters potentially involved in the production of novel bacteriocins were found in BAC3151, as well as biosynthetic genes of several other compounds, including non-ribosomal peptides, N-acyl homoserine lactonase and chitinases, revealing a genetic repertoire for antimicrobial synthesis greater than that of other Bacillus strains that have demonstrated effective activity against phytopathogens. This study showed for the first time that B. toyonensis has potential to produce various antimicrobials, and the analyses performed indicated that the endophytic strain BAC3151 can be useful for the development of new strategies to control microbial diseases in plants that are responsible for large damages in agricultural crops.     

Isolation,characterization and virulence of bacteria from <Emphasis Type="Italic">Ostrinia nubilalis</Emphasis> (Lepidoptera: Pyralidae)

Isolation, characterization and virulence of the culturable bacteria from entire tissues of larval Ostrinia nubilalis (Hübner) (Lepidoptera: Pyralidae) were studied to obtain new microbes for biological control. A total of 16 bacteria were isolated from living and dead larvae collected from different maize fields in the Eastern Black Sea Region of Turkey. The bacterial microbiota of O. nubilalis were identified as Pseudomonas aeruginosa (On1), Brevundimonas aurantiaca (On2), Chryseobacterium formosense (On3), Acinetobacter sp. (On4), Microbacterium thalassium (On5), Bacillus megaterium (On6), Serratia sp. (On7), Ochrobactrum sp. (On8), Variovorax paradoxus (On9), Corynebacterium glutamicum (On10), Paenibacillus sp. (On11), Alcaligenes faecalis (On12), Microbacterium testaceum (On13), Leucobacter sp. (On14), Leucobacter sp. (On15) and Serratia marcescens (On16) based on their morphological and biochemical characteristics. A partial sequence of the 16S rRNA gene was also determined to confirm strain identification. The highest insecticidal activities were obtained from P. aeruginosa On1 (80%), Serratia sp. On7 (60%), V. paradoxus On9 (50%) and S. marcescens On16 (50%) against larvae 14 days after treatment (p < 0.05). Also, the highest activity from previously isolated Bacillus species was observed from Bacillus thuringiensis subsp. tenebrionis Xd3 with 80% mortality within the same period (p < 0.05). Our results indicate that P. aeruginosa On1, Serratia sp. On7, V. paradoxus On9, S. marcescens On16 and B. thuringiensis subsp. tenebrionis Xd3 show potential for biocontrol of O. nubilalis.     

Molecular identification and control of endophytic contamination during in vitro plantlet development of <Emphasis Type="Italic">Fagonia indica</Emphasis>

Microbial contamination is the major cause of economic losses in commercial and scientific plant tissue culture laboratories. For successful micropropagation, it is important to control contamination during in vitro cultures. The present study was designed to isolate, identify and eradicate endophytic contaminants from in vitro cultures of medicinally important plant Fagonia indica. A total of eight distinct bacterial isolates from in vitro grown plantlets of F. indica were selected based on analysis of colony morphology. The endophytic bacterial contaminants identified at the species level through 16S rRNA sequence analysis were Enterobacter xiangfangensis, Bacillus vallismortis, Bacillus tequilensis, Terribacillus halophilus, Pantoea dispersa, Serratia marcescens subsp. Sakuensis, Staphylococcus epidermidis and Bacillus atrophaeus. It was observed that almost 60% of seedlings were contaminated with Bacillus sp. and out of those, Bacillus tequelensis contributed to most infections (70% out of the Bacillus infections). The other most frequently occurring bacteria were Bacillus vallismortis, Terribacillus halophilus and Serratia marcescens subsp. sakuensis. Furthermore, the addition of antimicrobials to the media either completely inhibited or drastically decreased the growth of endophytic bacteria as compared to the control in which 92% of the plantlets were contaminated with these endophytes. Nine different antibiotics (rifampicin, teicoplanin, gentamicin, vancomycin, ciprofloxacin, tobramycin, tetracycline, doxycycline and ampicillin) were tested for their activity against the identified endophytes. Antibiotics such as ciprofloxacin and tobramycin showed a good response and inhibited the growth of all the bacterial isolates at low doses compared to the other antibiotics. Tobramycin was the most effective as it inhibited the growth of five of the bacterial isolates at a dosage as low as 4 mg/L. In case of tetracycline (16 mg/L) and doxycycline (64 mg/L), the contamination frequency in plantlets was 25.6 and 45%, respectively. It is, therefore, important to search for more endophytes, causing adverse effects during in vitro cultures and should devise a feasible anti-microbial strategy for controlling such contamination.     

Endophytic microbes <Emphasis Type="Italic">Bacillus</Emphasis> sp. LZR216-regulated root development is dependent on polar auxin transport in <Emphasis Type="Italic">Arabidopsis</Emphasis> seedlings

Key message

Endophytic microbes Bacillus sp. LZR216 isolated from Arabidopsis root promoted Arabidopsis seedlings growth. It may be achieved by promoting the lateral root growth and inhibiting the primary root elongation.

Abstract

Plant roots are colonized by an immense number of microbes, including epiphytic and endophytic microbes. It was found that they have the ability to promote plant growth and protect roots from biotic and abiotic stresses. But little is known about the mechanism of the endophytic microbes-regulated root development. We isolated and identified a Bacillus sp., named as LZR216, of endophytic bacteria from Arabidopsis root. By employing a sterile experimental system, we found that LZR216 promoted the Arabidopsis seedlings growth, which may be achieved by promoting the lateral root growth and inhibiting the primary root elongation. By testing the cell type-specific developmental markers, we demonstrated that Bacillus sp. LZR216 increases the DR5::GUS and DR5::GFP expression but decreases the CYCB1;1::GUS expression in Arabidopsis root tips. Further studies indicated that LZR216 is able to inhibit the meristematic length and decrease the cell division capability but has little effect on the quiescent center function of the root meristem. Subsequently, it was also shown that LZR216 has no significant effects on the primary root length of the pin2 and aux1-7 mutants. Furthermore, LZR216 down-regulates the levels of PIN1-GFP, PIN2-GFP, PIN3-GFP, and AUX1-YFP. In addition, the wild-type Arabidopsis seedlings in the present of 1 or 5 µM NPA (an auxin transport inhibitor) were insensitive to LZR216-inhibited primary root elongation. Collectively, LZR216 regulates the development of root system architecture depending on polar auxin transport. This study shows a new insight on the ability of beneficial endophytic bacteria in regulating postembryonic root development.

     

Polyphasic taxonomic analysis of <Emphasis Type="Italic">Bacillus</Emphasis> sp. strain C6—the antagonist of phytopathogenic microorganisms

Polyphasic taxonomic analysis was carried out for Bacillus sp. strain C6, as the antagonist of phytopathogenic bacteria and micromycetes. The combination of cultural, morphological, physiological, and biochemical properties of the strain has enabled researchers to refer it to the Bacillus subtilis group. It has been shown that the fatty acids of the strain’s cell walls were predominantly represented by branched iso- and anteiso-C15:0 and C17:0 fatty acids (over 85%), which was typical for the Bacillus amyloliquefaciens species. The molecular genetic analysis carried out on the nucleotide sequence of the 16S rRNA gene, and the profiling of polymorphic nucleotides have enabled researchers to refer the strain in question to Bacillus amyloliquefaciens subsp. plantarum.     

<Emphasis Type="Italic">Bacillus</Emphasis> sp. strain M10 as a potential biocontrol agent protecting chili pepper and tomato fruits from anthracnose disease caused by <Emphasis Type="Italic">Colletotrichum capsici</Emphasis>

Bacillus sp. strain M10 was observed to produce an antifungal protein that inhibits the growth of Colletotrichum capsici, which is the causal agent of anthracnose disease of chili pepper and tomato. Ammonium sulfate precipitation, anion exchange chromatography, and sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the protein was approximately 55.4 kDa. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis and a subsequent sequence database search indicated the antifungal protein was most similar to the Bacillus amyloliquefaciens vegetative catalase (KatA) protein. Light microscopy observation revealed that the antifungal protein induced abnormal hyphal elongation and conidial swelling and rupture. The protein considerably inhibited anthracnose development and protected the fruits from C. capsici infection. Thus, Bacillus sp. strain M10 and/or its putative catalase may be useful as a post-harvest biocontrol agent that protects chili pepper and tomato fruits from anthracnose disease caused by C. capsici.     

Cytotoxic and toxicogenomic effects of silibinin in bladder cancer cells with different <Emphasis Type="Italic">TP53</Emphasis> status

Silibinin is a natural phenol found in the seeds of the milk thistle plant. Recent data have shown its effectiveness for preventing/treating bladder tumours. Therefore, in this study we investigated the cytotoxic and toxicogenetic activity of silibinin in bladder cancer cells with different TP53 statuses. Two bladder urothelial carcinoma cell lines were used: RT4 (wild-type TP53 gene) and T24 (mutated TP53 gene). Cell proliferation, clonogenic survival, apoptosis rates, genotoxicity and relative expression profile of FRAP/mTOR, FGFR3, AKT2 and DNMT1 genes and of miR100 and miR203 were evaluated. Silibinin promoted decreased proliferation and increased late apoptosis in TP53 mutated cells. Increased early apoptosis rates, primary DNA damage, and decrease of cell colonies in the clonogenic survival assay were detected in both RT4 and T24 cell lines. Down-regulation of FRAP/mTOR, AKT2, FGFR3, DNMT1 and miR100 expression occurred in RT4 cells. Modulation of miR203 was observed in both cell lines. In conclusion, despite the reduction of clone formation in both cell lines, the toxicogenomic effect of silibinin on FRAP/mTOR, AKT2, FGFR3, DNMT1 and miR100 was dependent on the TP53 status. Taken together, the data confirmed the role of silibinin as an antiproliferative compound, whose mechanism of action was related to the TP53 status.     

Physiological and proteomic analysis of plant growth enhancement by the rhizobacteria <Emphasis Type="Italic">Bacillus</Emphasis> sp. JS

In this study, the effects of the plant growth-promoting rhizobacterium (PGPR), Bacillus sp. JS on the growth of tobacco (Nicotiana tabacum ‘Xanthi’) and lettuce (Lactuca sativa ‘Crispa’), were evaluated by comparing various growth parameters between plants treated with the bacterium and those exposed to water or nutrient broth as control. In both tobacco and lettuce, fresh weight and length of shoots were increased upon exposure to Bacillus sp. JS. To explain the overall de novo expression of plant proteins by bacterial volatiles, two-dimensional gel electrophoresis was performed on samples from PGPR-treated tobacco plants. Our results showed that chlorophyll a/b binding proteins were significantly up-regulated, and total chlorophyll content was also increased. Our findings indicate the potential benefits of using Bacillus sp. JS as a growth-promoting factor in agricultural practice, and highlight the need for further research to explore these benefits.     

Inheritance and gene mapping of the white flower trait in <Emphasis Type="Italic">Brassica juncea</Emphasis>

Despite being a unique marker trait, white flower inheritance in Brassica juncea remains poorly understood at the gene level. In this study, we investigated a B. juncea landrace with white petal in China. The white petal phenotype possessed defective chromoplasts with less plastoglobuli than the yellow petal phenotype. Genetic analysis confirmed that two independent recessive genes (Bjpc1 and Bjpc2) controlled the white flower trait. We then mapped the BjPC1 gene in a BC₄ population comprising 2295 individuals. We identified seven AFLP (amplified fragment length polymorphism) markers closely linked to the white flower gene. BLAST search revealed the sequence of AFLP fragments were highly homologous with the Scaffold000085 and Scaffold000031 sequences on the A02 chromosome in the Brassica rapa genome. Based on this sequence homology, we developed simple sequence repeat (SSR) primer pairs and identified 13 SSRs linked to the BjPC1 gene, including two that were co-segregated (SSR9 and SSR10). The two closest markers (SSR4 and SSR11) were respectively 0.9 and 0.4 cM on either side of BjPC1. BLAST analysis revealed that these marker sequences corresponded highly to A02 in B. juncea. They were mapped within a 33 kb genomic region on B. rapa A02 (corresponds to a 40 kb genomic region on B. juncea A02) that included three genes. Sequence BjuA008406, homologous to AtPES2 in Arabidopsis thaliana and Bra032956 in B. rapa, was the most likely candidate for BjPC1. These results should accelerate BjPC1 cloning and facilitate our understanding of the molecular mechanisms controlling B. juncea petal color.