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Sigma factor 70 RpoD contributes to virulence by regulating cell motility, oxidative stress tolerance, and manipulating the expression of hrpG and hrpX in Xanthomonas oryzae pv. oryzae

Zhizhou Xu, Guichun Wu, Bo Wang, Baodian Guo, Cong Sheng, Yangyang Zhao, Bao Tang, Yancun Zhao, Fengquan Liu

2025, 24 (5): 1844-1859. DOI: 10.1016/j.jia.2023.10.017

Abstract （85） PDF in ScienceDirect

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight in rice, which reduces crop yield and leads to significant economic losses. Bacterial sigma (σ) factors are highly specialized proteins that allow RNA polymerase to recognize and bind to specific promoters. σ⁷⁰ factors also regulate the expression of genes involved in stress response and virulence. However, the role of RpoD in Xoo is still unclear. In this study, we found that σ⁷⁰ factor RpoD is quite conservative among phytopathogenic bacteria, especially in Xanthomonas sp. In Xoo, PXO_RpoD plays an important role in oxidative stress tolerance and cell motility, as well as being essential for full virulence. Cleavage under targets and tagmentation (CUT&Tag) analyses indicated that RpoD mediates the type three secretion system (T3SS) by regulating the regulation of hrpG and hrpX. By performing bacterial one-hybrid and electrophoretic mobility assay (EMSA), we observed that RpoD directly bound to the promoters of hrpG and hrpX. Collectively, these results demonstrate the transcriptional mechanism and pathogenic functions of RpoD in regulating cell motility and oxidative stress response, providing novel insights into potential targets for disease control.

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Multi-nutrient fertilization-based analysis of fruit quality and mineral element composition during fruit development in Merlot wine grapevines

Xiaolong Wang, Xuedong Shao, Zhengwen Zhang, Xiaomin Zhong, Xiaohao Ji, Xiangbin Shi, Chang Liu, Zhiqiang Wang, Fengzhi Liu, Haibo Wang

2025, 24 (4): 1503-1514. DOI: 10.1016/j.jia.2024.04.032

Abstract （29） PDF in ScienceDirect

Mineral elements play a crucial role in plant growth and development. Ensuring the proper supply of these elements in the soil to maintain the optimum range within plants is necessary for achieving optimal fruit yield and quality. Unfortunately, the application of NPKCaMg fertilizers to fruit trees is often either insufficient or excessive, leading to environmental degradation and reduced fruit yield and quality. To assess the impacts of different fertilizers on the biological traits of grapes and their responses to nutritional elements, Merlot grapevines were subjected to multi-nutrient fertilization over four consecutive growing seasons from 2018 to 2021 in Penglai District, Yantai, China. Principal component analysis revealed that the T11 treatment, consisting of N₃P₃K₁Ca₂Mg₄, was the most suitable fertilizer type and application design among the treatments. The application of T11 resulted in a significantly lower (24.29–35.20%) fertilizer usage, and it resulted in increases in several important traits such as 100-grain weight (HGW), number of seeds (SN), total soluble solids (TSS), total seed phenols (SP), seed flavanols (SFI), and seed tannins (ST) by 3.28–12.84%, 3.76–20.03%, 1.11–14.95%, 2.16–23.69%, 11.00–32.78%, and 1.07–23.35%, respectively, compared to the T14 (N₄P₂K₃Ca₁Mg₄), T16 (N₄P₄K₁Ca₃Mg₂), T13 (N₄P₁K₄Ca₂Mg₃), and T15 (N₄P₃K₂Ca₄Mg₁) treatments. Flowering and fruiting processes exhibited a considerable demand for NPK, with higher requirements for K and B during fruit growth and development compared to the other macroelements and micronutrients, respectively. Excessive K in soil enhanced the competitive inhibition of Ca uptake by Merlot grapevines. The optimal ranges of mineral element contents for total peel phenols (PP), peel flavanols (PFI), total peel flavonoids (PFD), total seed phenols (SP), and seed tannins (ST) were primarily influenced by grape variety and nutritional analysis method. In conclusion, the careful selection of NPKCaMg fertilizer and its precise application to soil at an optimum range of mineral elements is critical for grapevine growth and development.

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A unique role of the pyrimidine de novo synthesis enzyme ODCase in Lysobacter enzymogenes

Mingming Yang, Yunxiao Tan, Jiabing Ma, Yingjia Zhao, Xia Yan, Nana Wang, Pingping Wang, Jiaqi Tan, Suilong Ai, Xiaofei Liang, Bangshuai Chang, Obadah E. A. Yousif, Chao Zhao, Bo Wang, Guoliang Qian, Lili Huang

2024, 23 (9): 3066-3077. DOI: 10.1016/j.jia.2023.11.047

Abstract （98） PDF in ScienceDirect

Bacterial species of the genus Lysobacter are environmentally ubiquitous with strong antifungal biocontrol potential. Heat-stable antifungal factor (HSAF) secreted by the biocontrol bacterium Lysobacter enzymogenes OH11 has broad-spectrum and highly efficient antifungal activity. Studying the biosynthetic regulations of HSAF would lay an important foundation for strain engineering toward improved HSAF production. In this work, we demonstrate that Le0752, an orotidine-5´-phosphate decarboxylase enzyme (ODCase) catalyzing a pivotal step of the UMP de novo biosynthesis pathway, is vital for HSAF-mediated antimicrobial activities and growth of L. enzymogenes OH11, but not for twitching motility. This gene regulates the production of HSAF by affecting the expression of lafB, a key gene in the HSAF biosynthesis operon, through the transcription factor Clp. Interestingly, bioinformatics analysis revealed that Le0752 belongs to the Group III ODCases, whereas its homologs in the closely related genera Xanthomonas and Stenotrophomonas belong to Group I, which contains most ODCases from Gram-positive bacteria, Gram-negative bacteria and cyanobacteria. Moreover, the Group I ODCase PXO_3614 from the Xanthomonas oryzae pv. oryzae PXO99^Astrain complemented the Le0752 mutant in regulating HSAF-mediated antagonistic activity. Together, these results highlight the important requirement of de novo pyrimidine biosynthetic enzymes for antibiotic HSAF production in L. enzymogenes, which lays an important foundation for improving HSAF production via metabolic flow design and for dissecting the regulatory functions of bacterial ODCases.

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Hatching and development of maize cyst nematode Heterodera zeae infecting different plant hosts

Jiangkuan Cui, Haohao Ren, Bo Wang, Fujie Chang, Xuehai Zhang, Haoguang Meng, Shijun Jiang, Jihua Tang

2024, 23 (5): 1593-1603. DOI: 10.1016/j.jia.2023.04.042

Abstract （187） PDF in ScienceDirect

The occurrence, distribution, and rapid molecular detection technology of Heterodera zeae Koshy et al. 1971, have been reported in China. We explored the biological characteristics of H. zeae sampled in Henan Province, China to understand its interaction with plants. Cysts and second-stage juveniles (J2s) were identified under an optical and scanning electron microscope, internal transcribed spacer (ITS) phylogenetic tree, and sequence characterized amplified region (SCAR)-PCR analyses. The optimum hatching temperatures of H. zeae were 30°C and 28°C, with cumulative hatching rates of 16.5 and 16.1%, respectively, at 30 days post-hatching (dph). The hatching rate of H. zeae eggs was improved by 20- and 50-time maize soil leachate and root juice, and 10-time root exudates. The hatching rate in 10-time root exudates was the highest (25.9%). The 10-time root exudates of maize and millet produced the highest hatching rate at 30 dph (25.9 and 22.9%, respectively), followed by wheat (19.9%), barley (18.3%), and rice (17.6%). Heterodera zeae developed faster in maize than in other crops. Fourth-stage juveniles (J4s) were detected in maize roots 8 days post-inoculation (dpi) at 28°C but not in other crops. Combined with hatching tests, the Huang–Huai–Hai summer maize region and the south and central-southwest mountainous maize areas are highly suitable for H. zeae in China. This is the first systematically study of the hatching and infection characteristics on different plant hosts of corn cyst nematode H. zeae in temperate regions. This study laid a theoretical foundation for the rapid spread and high environmental adaptability of corn cyst nematode.

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Retinol is involved in the intestinal regeneration and strengthens the intestinal barrier during refeeding in broiler chickens

Youli Wang, Huajin Zhou, Jing Chen, Yuqin Wu, Yuming Guo, Bo Wang, Jianmin Yuan

2024, 23 (11): 3843-3859. DOI: 10.1016/j.jia.2023.11.006

Abstract （99） PDF in ScienceDirect

Fasting is typically used before feeding metabolizable energy assessment in broilers. Previous studies have shown that fasting cause atrophy of the intestinal villus. Whether fasting affects intestinal permeability during refeeding by altering barrier function and nutrient absorption is of concern. Here, 23-d-old broilers were randomly assigned to 5 treatments, fasted for 0, 12, 24, 36, and 48 h, respectively, and then refed for 2 d, to study the impact of different duration of fasting on the intestinal regeneration and barrier function during refeeding. Results showed that the intestinal morphology in fasted birds was recovered in 2 d of refeeding at most. As fasting durations increased, enterocytes per intestinal villus were linearly and quadratically increased (both P<0.05), whereas goblet cells per intestinal villus was linearly decreased (both P<0.05). Besides, the mRNA level of lysozyme was linearly decreased as fasting durations increased during refeeding (both P<0.05), while quadratically increased mucin 2 was observed only after 1 d of refeeding (P<0.05). Linear increase effects were observed for claudin 2 and zonula occludens-1 with increased fasting durations after 1 d of refeeding (all P<0.05), and linear and quadratical effects were observed for claudin 2 at 2 d of refeeding (both P<0.05). Besides, we found that intestinal permeability to creatinine, 4 and 70 kD dextran were linearly and quadratically decreased with increased fasting durations at 6 h and 1 d of refeeding (all P<0.05). Furthermore, jejunum proteomic from birds refed for 6 h showed that birds fasted for 36 h showed increased antimicrobial peptides and upregulated retinol metabolism when compared to the nonfasted birds (P<0.05). Further study showed that retinyl ester catabolism was inhibited during fasting and enhanced during refeeding. Results of intestinal organoid culture showed that retinol benefits the cell proliferation and enterocyte differentiation. In conclusion, the intestinal permeability to small and large molecules was decreased during refeeding by strengthening the intestinal barrier function, and the activated retinol metabolism during refeeding is involved in the intestinal regeneration and strengthens the intestinal barrier.

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Nicotinamide mononucleotide confers broad-spectrum disease resistance in plants

Shuangxi Zhang, Xinlin Wei, Rongbo Wang, Hejing Shen, Hehuan You, Langjun Cui, Yi Qiang, Peiqing Liu, Meixiang Zhang, Yuyan An

DOI: 10.1016/j.jia.2024.04.027 Online: 23 May 2024

Abstract （58） PDF in ScienceDirect

Nicotinamide mononucleotide (NMN), a precursor in nicotinamide adenine dinucleotide (NAD) biosynthesis, has long been recognized for its pivotal role in medicine. Recent investigations have suggested its potential as a plant immunity inducer for controlling fungal diseases. However, whether NMN confers plant broad-spectrum resistance against diverse phytopathogens, and its underlying mechanisms remain ambiguous. In this study, we investigate the effect of NMN against multiple phytopathogens in tobacco. Our results demonstrate that tobacco pretreated with NMN exhibits enhanced resistance against Rastonia solanacearum CQPS-1, Pseudomonas syringae DC3000 ∆hopQ1-1, Phytophthora parasitica, and tobacco mosaic virus (TMV). NMN displays effectiveness within the concentration range of 50-600 μM, with 75 μM NMN exhibiting the most pronounced effect. The impact of NMN pretreatment could persist for up to 10 days. Beyond tobacco, NMN pretreatment enhances disease resistance in tomato and pepper plants against diverse pathogens, underscoring NMN’s capacity to confer broad-spectrum disease resistance in crops. Moreover, RT-qPCR analysis reveals that NMN significantly upregulates the expression of the pattern-triggered immunity (PTI) marker gene NbCYP71D20 and salicylic acid (SA) marker gene NbPR1a. This suggests that NMN enhances plant resistance by inducing both PTI and SA-mediated immunity. Interestingly, the positive impact of NMN on plant disease resistance is not significantly compromised in both NMN adenylyltransferase (NMNAT)-silenced plants and NAD receptor mutant lecrk-I.8, suggesting the existence of NAD-independent signaling pathways for NMN-induced plant immunity. In conclusion, our study establishes that the bioactive molecule NMN imparts broad-spectrum disease resistance in plants, offering a simple, environmental-friendly, and promising strategy for safeguarding crops against diverse phytopathogens. These findings also provide valuable insights for future in-depth studies into the functional mechanisms of NMN.

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