RNA-Seq revealed that infection with white tip nematodes could downregulate rice photosynthetic genes

Overexpression of Abscisic Acid Biosynthesis Gene OsNCED3 Enhances Survival Rate and Tolerance to Alkaline Stress in Rice Seedlings

Alkaline stress with high pH levels could significantly influence plant growth and survival. The enzyme 9-cis-epoxycarotenoid dioxygenase (NCED) serves as a critical bottleneck in the biosynthesis of abscisic acid (ABA), making it essential for regulating stress tolerance. Here, we show that OsNCED3-overexpressing rice lines have increased ABA content by up to 50.90% and improved transcription levels of numerous genes involved in stress responses that significantly enhance seedling survival rates. Overexpression of OsNCED3 increased the dry weight contents of the total chlorophyll, proline, soluble sugar, starch, and the activities of antioxidant enzymes of rice seedlings, while reducing the contents of O2·-, H2O2, and malondialdehyde under hydroponic alkaline stress conditions simulated by 10, 15, and 20 mmol L-1 of Na2CO3. Additionally, the OsNCED3-overexpressing rice lines exhibited a notable increase in the expression of OsNCED3; ABA response-related genes OsSalT and OsWsi18; ion homeostasis-related genes OsAKT1, OsHKT1;5, OsSOS1, and OsNHX5; and ROS scavenging-related genes OsCu/Zn-SOD, OsFe-SOD, OsPOX1, OsCATA, OsCATB, and OsAPX1 in rice seedling leaves. The results of these findings suggest that overexpression of OsNCED3 upregulates endogenous ABA levels and the expression of stress response genes, which represents an innovative molecular approach for enhancing the alkaline tolerance of rice seedlings.

Sorghum root epigenetic landscape during limiting phosphorus conditions

Efficient acquisition and use of available phosphorus from the soil is crucial for plant growth, development, and yield. With an ever-increasing acreage of croplands with suboptimal available soil phosphorus, genetic improvement of sorghum germplasm for enhanced phosphorus acquisition from soil is crucial to increasing agricultural output and reducing inputs, while confronted with a growing world population and uncertain climate. Sorghum bicolor is a globally important commodity for food, fodder, and forage. Known for robust tolerance to heat, drought, and other abiotic stresses, its capacity for optimal phosphorus use efficiency (PUE) is still being investigated for optimized root system architectures (RSA). Whilst a few RSA-influencing genes have been identified in sorghum and other grasses, the epigenetic impact on expression and tissue-specific activation of candidate PUE genes remains elusive. Here, we present transcriptomic, epigenetic, and regulatory network profiling of RSA modulation in the BTx623 sorghum background in response to limiting phosphorus (LP) conditions. We show that during LP, sorghum RSA is remodeled to increase root length and surface area, likely enhancing its ability to acquire P. Global DNA 5-methylcytosine and H3K4 and H3K27 trimethylation levels decrease in response to LP, while H3K4me3 peaks and DNA hypomethylated regions contain recognition motifs of numerous developmental and nutrient responsive transcription factors that display disparate expression patterns between different root tissues (primary root apex, elongation zone, and lateral root apex).

A novel ATPase gene, Ab-atps, plays an important role in the interaction of rice and white tip nematode, Aphelenchoides besseyi

Plant kinases containing the LysM domain play important roles in pathogen recognition and self-defense reactions. And it could recognize microbe-associated molecules including chitin and other polypeptides. The white tip nematode Aphelenchoides besseyi is a migratory parasitic nematode that infects plant shoots. It is distributed over almost all rice-producing areas and causes up to 50% economic losses. The rice OsRLK3 gene was a defense-related LysM kinase gene of rice. This study showed that the rice LysM kinase OsRLK3 could be induced by flg22, jasmonic acid, salicylic acid, and chitin. An interaction gene, Ab-atps from A. besseyi, was identified by screening the interaction between the rice gene OsRLK3 and an A. besseyi cDNA library using yeast two-hybrid screening. Ab-atps is a novel ATP synthase gene with a full length of 1341 bp, coding for 183 amino acids. The mRNA of Ab-atps was located in the esophagus and reproductive system of A. besseyi. The expression of Ab-atps was assessed at different developmental stages of the nematode and found to be the highest in the juvenile, followed by the egg, female, and male. Reproduction was significantly decreased in nematodes treated with Ab-atps double-stranded RNA (dsRNA) (p < 0.05). Transient expression experiments showed that Ab-ATPS-GFP was distributed in the nucleus, cytoplasm, and cell membrane, and Ab-ATPS-GFP triggered plant cell death. OsRLK3 was expressed significantly higher at 0.5 day and 1 day (p < 0.05) in rice plants inoculated with nematodes treated with Ab-atps dsRNA and gfp dsRNA for 0.5-7 days, respectively. Further, OsRLK3 expression under Ab-atps dsRNA treatment was significantly lower than with gfp dsRNA treatment at 0.5 day (p < 0.05) and significantly higher than with gfp dsRNA treatment at 1 day (p < 0.05). These results suggest that rice OsRLK3 could interact with A. besseyi Ab-atps, which plays an important role in growth, reproduction, and infection of the nematode. Our findings provide a theoretical basis to further understand the parasitic strategy of A. besseyi and its interaction mechanism with host plants, suggesting new ideas and targets for controlling A. besseyi.

The influence of competing root symbionts on below-ground plant resource allocation

Plants typically interact with multiple above- and below-ground organisms simultaneously, with their symbiotic relationships spanning a continuum ranging from mutualism, such as with arbuscular mycorrhizal fungi (AMF), to parasitism, including symbioses with plant-parasitic nematodes (PPN).Although research is revealing the patterns of plant resource allocation to mutualistic AMF partners under different host and environmental constraints, the root ecosystem, with multiple competing symbionts, is often ignored. Such competition is likely to heavily influence resource allocation to symbionts.Here, we outline and discuss the competition between AMF and PPN for the finite supply of host plant resources, highlighting the need for a more holistic understanding of the influence of below-ground interactions on plant resource allocation. Based on recent developments in our understanding of other symbiotic systems such as legume-rhizobia and AMF-aphid-plant, we propose hypotheses for the distribution of plant resources between contrasting below-ground symbionts and how such competition may affect the host.We identify relevant knowledge gaps at the physiological and molecular scales which, if resolved, will improve our understanding of the true ecological significance and potential future exploitation of AMF-PPN-plant interactions in order to optimize plant growth. To resolve these outstanding knowledge gaps, we propose the application of well-established methods in isotope tracing and nutrient budgeting to monitor the movement of nutrients between symbionts. By combining these approaches with novel time of arrival experiments and experimental systems involving multiple plant hosts interlinked by common mycelial networks, it may be possible to reveal the impact of multiple, simultaneous colonizations by competing symbionts on carbon and nutrient flows across ecologically important scales.

A genome-wide survey of interaction between rice and Magnaporthe oryzae via microarray analysis

The main aim of the work is to study the regulation of gene expression in the interaction between rice and Magnaporthe oryzae by gene chip technology. In this study, we mainly focused on changes of gene expression at 24, 48, and 72 hours post-inoculation (hpi), through which we could conduct a more comprehensive analysis of rice blast-related genes in the process of infection. The results showed that the experimental groups contained 460, 1227, and 3937 significant differentially expressed genes at 24, 48, and 72 hpi, respectively. Furthermore, 115 significantly differentially expressed genes were identified in response to rice blast infection at all three time points. By annotating these 115 genes, they were divided into three categories: metabolic pathways, proteins or enzymes, and organelle components. As expected, many of these genes were known rice blast-related genes; however, we discovered new genes with high fold changes. Most of them encoded conserved hypothetical proteins, and some were hypothetically conserved genes. Our study may contribute to finding new resistance genes and understanding the mechanism of rice blast development.

Diverse Roles of MAX1 Homologues in Rice

Cytochrome P450 enzymes encoded by MORE AXILLARY GROWTH1 (MAX1)-like genes produce most of the structural diversity of strigolactones during the final steps of strigolactone biosynthesis. The diverse copies of MAX1 in Oryza sativa provide a resource to investigate why plants produce such a wide range of strigolactones. Here we performed in silico analyses of transcription factors and microRNAs that may regulate each rice MAX1, and compared the results with available data about MAX1 expression profiles and genes co-expressed with MAX1 genes. Data suggest that distinct mechanisms regulate the expression of each MAX1. Moreover, there may be novel functions for MAX1 homologues, such as the regulation of flower development or responses to heavy metals. In addition, individual MAX1s could be involved in specific functions, such as the regulation of seed development or wax synthesis in rice. Our analysis reveals potential new avenues of strigolactone research that may otherwise not be obvious.

An overview of the transcriptional responses of two tolerant and susceptible sugarcane cultivars to borer (Diatraea saccharalis) infestation

Diatraea saccharalis constitutes a threat to the sugarcane productivity, and obtaining borer tolerant cultivars is an alternative method of control. Although there are studies about the relationship between the interaction of D. saccharalis with sugarcane, little is known about the molecular and genomic basis of defense mechanisms that confer tolerance to sugarcane cultivars. Here, we analyzed the transcriptional profile of two sugarcane cultivars in response to borer attack, RB867515 and SP80-3280, which are considered tolerant and sensitive to the borer attack, respectively. A sugarcane genome and transcriptome were used for read mapping. Differentially expressed transcripts and genes were identified and termed to as DETs and DEGs, according to the sugarcane database adopted. A total of 745 DETs and 416 DEGs were identified (log₂|ratio| > 0.81; FDR corrected P value ≤ 0.01) after borer infestation. Following annotation of up- and down-regulated DETs and DEGs by similarity searches, the sugarcane cultivars demonstrated an up-regulation of jasmonic acid (JA), ethylene (ET), and defense protein genes, as well as a down-regulation of pathways involved in photosynthesis and energy metabolism. The expression analysis also highlighted that RB867515 cultivar is possibly more transcriptionally activated after 12 h from infestation than SP80-3280, which could imply in quicker responses by probably triggering more defense-related genes and mediating metabolic pathways to cope with borer attack.