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Bacillus subtilis strain Ydj3 was applied to sweet peppers to understand the influence of this bacterium on the growth, fruit quality, and rhizosphere microbial composition of sweet pepper. The promotion of seed germination was observed for sweet pepper seeds treated with the Ydj3 strain, indicating that Ydj3 promoted seed germination and daily germination speed (131.5 ± 10.8 seeds/day) compared with the control (73.8 ± 2.5 seeds/day). Strain Ydj3 displayed chemotaxis toward root exudates from sweet pepper and could colonize the roots, which enhanced root hair growth. Following the one-per-month application of strain Ydj3 to sweet pepper grown in a commercial greenhouse, the yield, fruit weight, and vitamin C content significantly increased compared with those of the control. Additionally, the composition of the rhizosphere bacterial community of sweet pepper changed considerably, with the Bacillus genus becoming the most dominant bacterial genus in the treated group. These results suggested that B . subtilis Ydj3 promotes seed germination and enhances fruit quality, particularly the vitamin C content, of sweet pepper. These effects may be partly attributed to the B . subtilis Ydj3 colonization of sweet pepper roots due to Ydj3 chemotaxis toward root exudates, resulting in the modulation of the rhizosphere bacterial community.

Summary A major challenge of modern agricultural biotechnology is the optimization of plant architecture for enhanced productivity, stress tolerance and water use efficiency (WUE). To optimize plant height and tillering that directly link to grain yield in cereals and are known to be tightly regulated by gibberellins (GAs), we attenuated the endogenous levels of GAs in rice via its degradation. GA 2‐oxidase (GA2ox) is a key enzyme that inactivates endogenous GAs and their precursors. We identified three conserved domains in a unique class of C20 GA2ox, GA2ox6, which is known to regulate the architecture and function of rice plants. We mutated nine specific amino acids in these conserved domains and observed a gradient of effects on plant height. Ectopic expression of some of these GA2ox6 mutants moderately lowered GA levels and reprogrammed transcriptional networks, leading to reduced plant height, more productive tillers, expanded root system, higher WUE and photosynthesis rate, and elevated abiotic and biotic stress tolerance in transgenic rice. Combinations of these beneficial traits conferred not only drought and disease tolerance but also increased grain yield by 10–30% in field trials. Our studies hold the promise of manipulating GA levels to substantially improve plant architecture, stress tolerance and grain yield in rice and possibly in other major crops.

Bacterial fruit blotch, caused by the seedborne gram-negative bacterium Acidovorax citrulli , is one of the most destructive bacterial diseases of cucurbits (gourds) worldwide. Despite its prevalence, effective and reliable means to control bacterial fruit blotch remain limited. Transcriptomic analyses of tissue culture-based regeneration processes have revealed that organogenesis-associated cellular reprogramming is often associated with upregulation of stress- and defense-responsive genes. Yet, there is limited evidence supporting the notion that the reprogrammed cellular metabolism of the regenerated tissued confers bona fide antimicrobial activity. Here, we explored the anti-bacterial activity of protocorm-like-bodies (PLBs) of Phalaenopsis aphrodite . Encouragingly, we found that the PLB extract was potent in slowing growth of A. citrulli , reducing the number of bacteria attached to watermelon seeds, and alleviating disease symptoms of watermelon seedlings caused by A. citrulli . Because the anti-bacterial activity can be fractionated chemically, we predict that reprogrammed cellular activity during the PLB regeneration process produces metabolites with antibacterial activity. In conclusion, our data demonstrated the antibacterial activity in developing PLBs and revealed the potential of using orchid PLBs to discover chemicals to control bacterial fruit blotch disease.

Citrus bacterial canker caused by Xanthomonas axonopodis pv. citri is a devastating disease resulting in significant crop losses in various citrus cultivars worldwide. A biocontrol agent has not been recommended for this disease. To explore the potential of bacilli native to Taiwan to control this disease, Bacillus species with a broad spectrum of antagonistic activity against various phytopathogens were isolated from plant potting mixes, organic compost and the rhizosphere soil. Seven strains TKS1-1, OF3-16, SP4-17, HSP1, WG6-14, TLB7-7, and WP8-12 showing superior antagonistic activity were chosen for biopesticide development. The genetic identity based on 16S rDNA sequences indicated that all seven native strains were close relatives of the B. subtilis group and appeared to be discrete from the B. cereus group. DNA polymorphisms in strains WG6-14, SP4-17, TKS1-1, and WP8-12, as revealed by repetitive sequence-based PCR with the BOXA1R primers were similar to each other, but different from those of the respective Bacillus type strains. However, molecular typing of the strains using either tDNA-intergenic spacer regions or 16S-23S intergenic transcribed spacer regions was unable to differentiate the strains at the species level. Strains TKS1-1 and WG6-14 attenuated symptom development of citrus bacterial canker, which was found to be correlated with a reduction in colonization and biofilm formation by X. axonopodis pv. citri on leaf surfaces. The application of a Bacillus strain TKS1-1 endospore formulation to the leaf surfaces of citrus reduced the incidence of citrus bacterial canker and could prevent development of the disease.

There have been few studies investigating interactions of G-protein beta3 subunit (GNB3) C825T (rs5443) and dietary sodium intake on the risk of hypertension, i.e., BP salt sensitivity. The study aims to evaluate joint effects of GNB3 polymorphisms and sodium consumption on the development of hypertension. A cohort-based case-control study was conducted in 2014. There are 233 participants with newly diagnosed hypertension in the case group and 699 participants in the gender-matched control group. The primary outcome is the development of hypertension over a 10-year period. The determinants of hypertension were three genotypes of SNP in GNB3 (TT; CT; and CC) and two dietary salt categories on the basis of the level of sodium consumption representing high (>4800 mg/day) and low-sodium (<2400 mg/day) diets. The development of hypertension increased with participants carrying TT genotype and high-sodium diets comparing with those carrying TC or CC genotype with low-sodium diets (adjusted OR 3.23, 95% CI 1.52–6.83) (Rothman synergy index = 3.79). The study suggests that GNB3 C825T polymorphism may influence the response of the renin-angiotensin system to high-sodium diet. It implies that GNB3 can be served as an easy, inexpensive, and early genetic marker of salt sensitivity to blood pressure. Salt-sensitive individuals should pay more attention to salt intake to reduce cardiovascular morbidity or mortality.

Citrus bacterial canker caused by Xanthomonas axonopodis pv. citri is a serious disease that impacts citrus production worldwide, and X. axonopodis pv. citri is listed as a quarantine pest in certain countries. Biofilm formation is important for the successful development of a pathogenic relationship between various bacteria and their host(s). To understand the mechanisms of biofilm formation by X. axonopodis pv. citri strain XW19, the strain was subjected to transposon mutagenesis. One mutant with a mutation in a two-component response regulator gene that was deficient in biofilm formation on a polystyrene microplate was selected for further study. The protein was designated as BfdR for biofilm formation defective regulator. BfdR from strain XW19 shares 100% amino acid sequence identity with XAC1284 of X. axonopodis pv. citri strain 306 and 30-100% identity with two-component response regulators in various pathogens and environmental microorganisms. The bfdR mutant strain exhibited significantly decreased biofilm formation on the leaf surfaces of Mexican lime compared with the wild type strain. The bfdR mutant was also compromised in its ability to cause canker lesions. The wild-type phenotype was restored by providing pbfdR in trans in the bfdR mutant. Our data indicated that BfdR did not regulate the production of virulence-related extracellular enzymes including amylase, lipase, protease, and lecithinase or the expression of hrpG, rfbC, and katE; however, BfdR controlled the expression of rpfF in XVM2 medium, which mimics cytoplasmic fluids in planta. In conclusion, biofilm formation on leaf surfaces of citrus is important for canker development in X. axonopodis pv. citri XW19. The process is controlled by the two-component response regulator BfdR via regulation of rpfF, which is required for the biosynthesis of a diffusible signal factor.

Bacillus subtilis strain Ydj3 was applied to sweet peppers to understand the influence of this bacterium on the growth, fruit quality, and rhizosphere microbial composition of sweet pepper. The promotion of seed germination was observed for sweet pepper seeds treated with the Ydj3 strain, indicating that Ydj3 promoted seed germination and daily germination speed (131.5 ± 10.8 seeds/day) compared with the control (73.8 ± 2.5 seeds/day). Strain Ydj3 displayed chemotaxis toward root exudates from sweet pepper and could colonize the roots, which enhanced root hair growth. Following the one-per-month application of strain Ydj3 to sweet pepper grown in a commercial greenhouse, the yield, fruit weight, and vitamin C content significantly increased compared with those of the control. Additionally, the composition of the rhizosphere bacterial community of sweet pepper changed considerably, with the Bacillus genus becoming the most dominant bacterial genus in the treated group. These results suggested that B. subtilis Ydj3 promotes seed germination and enhances fruit quality, particularly the vitamin C content, of sweet pepper. These effects may be partly attributed to the B. subtilis Ydj3 colonization of sweet pepper roots due to Ydj3 chemotaxis toward root exudates, resulting in the modulation of the rhizosphere bacterial community.

Cabbage is an important vegetable crop worldwide. In Taiwan, during cabbage production, bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum often leads to significant yield losses. Aligning with the Sustainable Development Goals, there is a high demand for sustainable disease control strategies. Silicates are considered to be effective elicitors in activating plant defense responses and are reported to improve resistance to certain plant diseases. Bacillus amyloliquefaciens PMB05 fermentation liquid has been shown to enhance plant immunity and control many bacterial diseases. The supplementation of silicates to the PMB05 fermentation liquid may further improve its efficacy to control bacterial soft rot in cabbage. This study evaluated the effects of sodium metasilicate and potassium silicate on PMB05-mediated plant immune responses and disease control. Initial assays confirmed that treatment with B. amyloliquefaciens PMB05 suspension significantly increased HrpN-triggered reactive oxygen species (ROS) generation and callose deposition; moreover, PMB05 treatment alone reduced bacterial soft rot severity by 39.7%. When combined with B. amyloliquefaceins PMB05 fermentation liquid, sodium metasilicate at 2000 μM further enhanced ROS generation and callose deposition by 100% and 133%, respectively, compared to the treatment of PMB05 alone (p < 0.05). In contrast, potassium silicate exhibited inconsistent effects on ROS production, with both 500 and 1000 µM concentrations significantly reducing ROS generation by 26% and 38%, respectively, while none of the tested concentrations affected callose deposition (p < 0.05). Lastly, disease severity assessments in cabbage inoculated with P. carotovorum subsp. carotovorum PCCSB1 revealed that B. amyloliquefaciens PMB05 fermentation liquid was able to reduce bacterial soft rot symptoms by 60.3%. Supplementation with 1500 and 2000 µM sodium metasilicate further decreased disease severity by 77.9% and 76.4%, respectively (p < 0.05). Although the supplementation of potassium silicate also significantly reduced disease severity compared to P. carotovorum subsp. carotovorum PCCSB1 alone, it was less effective than PMB05 fermentation alone. Overall, these results demonstrate that sodium metasilicate enhances the biocontrol activity of B. amyloliquefaciens PMB05 by further intensifying plant immune responses. This approach may broaden the large-scale use of B. amyloliquefaciens PMB05 fermentation liquid for sustainable soft rot management in cabbage, although the stability and cost-effectiveness of sodium metasilicate under field conditions still require validation.

Xylella fastidiosa causes Pierce's disease (PD) and is transmitted by xylem-sap-feeding insects. While X. fastidiosa-infected grapevines have been detected, the transmission vectors reported have never been recorded in Taiwan. Previous studies have suggested that Kolla paulula (Walker) and Bothrogonia ferruginea (F.) are candidate vectors in Taiwan. Here, we explored the life history of these two leafhoppers, evaluated the transmission efficiency of X. fastidiosa by the vectors, and investigated the genetic identity of three collected X. fastidiosa strains, namely, GMb, BQa, and BQ7f from the grapevine cultivars Golden Muscat (GM) and Black Queen (BQ), and one previously extracted strain GV148 from Kyoho (GV) showing PD symptoms in local vineyards. The results showed that all four strains were 100% identical to X. fastidiosa isolate Temecula1 from a naturally infected grapevine in the United States based on sequence analyses of 16S rRNA and 16S-23S ITS. The acquisition rates by K. paulula and B. ferruginea from the symptomatic cultivar Golden Muscat were 83.3 and 70.0% per individual, and the transmission rates to healthy grapevines were 13.3 and 6.7%, respectively. The acquisition rates by the groups of three K. paulula from the symptomatic cultivars Golden Muscat and Black Queen were 54.7 and 49.6%, respectively. Additionally, the transmission rates by K. paulula from and to each of these two grapevine cultivars were not significantly different. In view of their acquisition from infected grapevines and the effective transmission of X. fastidiosa to healthy grapevines, these two sharpshooter species are vectors of X. fastidiosa in Taiwan.