Rice Science最新文献

Given the consistent release of zinc oxide (ZnO) nanoparticles into the environment, it is urgent to study their impact on plants in depth. In this study, grains of rice were treated with two different concentrations of ZnO nanoparticles (NP-ZnO, 10 and 100 mg/L), and their bulk counterpart (B-ZnO) were used to evaluate whether ZnO action could depend on particle size. To test this hypothesis, root growth and development assessment, oxidative stress parameters, indole-3-acetic acid (IAA) content and molecules/enzymes involved in IAA metabolism were analyzed. In situ localization of Zn in control and treated roots was also performed. Though Zn was visible inside root cells only following nanoparticle treatment, both materials (NP-ZnO and B-ZnO) were able to affect seedling growth and root morphology, with alteration in the concentration/pattern of localization of oxidative stress markers and with a different action depending on particle size. In addition, only ZnO supplied as bulk material induced a significant increase in both IAA concentration and lateral root density, supporting our hypothesis that bulk particles might enhance lateral root development through the rise of IAA concentration. Apparently, IAA concentration was influenced more by the activity of the catabolic peroxidases than by the protective action of phenols.

Ustiloxins are vital cyclopeptide mycotoxins originally isolated from rice false smut balls that form in rice spikelets infected by the fungal pathogen Ustilaginoidea virens. The toxicity of the water extract of rice false smut balls (RBWE) remains to be investigated. Studies have shown that RBWE may be toxic to animals, but toxicological evidence is still lacking. In this study, we found that the IC₅₀ values of RBWE to BNL CL.2 cells at 24 and 48 h were 40.02 and 30.11 μg/mL, respectively, with positive correlations with dose toxicity and time toxicity. After treatment with RBWE, the number of BNL CL.2 cells decreased significantly, and the morphology of BNL CL.2 cells showed atrophy and wall detachment. RBWE induced DNA presynthesis phase arrest of BNL CL.2 cells, increased the proportion of apoptotic cells and inhibited cell proliferation. RBWE up-regulated reactive oxygen species (ROS) levels and lowered mitochondrial membrane potentials. Additionally, Western blot and qRT-PCR results suggested that RBWE exerted the above effects by promoting the Nrf2/HO-1 and caspase-induced apoptosis pathways in vitro and in vivo. The contents of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and total bile acids in the serum of mice from Institute of Cancer were significantly up-regulated by RBWE. At the same time, RBWE can lead to increases in ROS and malondialdehyde contents, decreases in contents of oxidized glutathione, glutathione and reduced glutathione, as well as decrease in catalase and superoxide dismutase activities in mouse liver tissues, demonstrating that oxidative stress occurred in mice. Moreover, liver damage was further detected by haematoxylin-eosin staining and electron microscopy to verify the damage to the mice caused by RBWE. In general, RBWE may cause hepatotoxicity in vivo and in vitro via the apoptosis pathway, which provides a reference for hepatotoxicity and its mechanism of action.

This investigation aimed to establish the geographical traceability of Malaysian rice by assessing the elemental composition in paddy soil. Multi-element determination in combination with a chemometric approach was applied to evaluate the elemental concentrations of paddy soil from granaries cultivated with the same rice variety and to assess the relationship between elements in the soil and rice (SAR) system. A total of 29 elements (aluminum, arsenic, barium, bromine, calcium, chlorine, cobalt, chromium, cesium, europium, iron, gallium, hafnium, potassium, lanthanum, lutetium, magnesium, manganese, sodium, rubidium, antimony, scandium, samarium, thorium, titanium, uranium, vanadium, ytterbium and zinc) were successfully determined in paddy soil from Kedah, Selangor and Langkawi by neutron activation analysis. A significant difference (P < 0.05) between 18 elements in the soil samples was obtained. The chemometric approaches of principal component and linear discriminant analyses demonstrated clear discrimination and highly corrected classification (100%) of the soil samples. A high classification (98.1%) was also achieved by assessing 10 elements (aluminum, arsenic, bromine, chlorine, potassium, magnesium, manganese, sodium, rubidium and zinc), which similarly applied to rice geographical origin determination. Similar elements in SAR were also observed for differences in the pattern of correlation and bioaccumulation factor between the granaries. Furthermore, the generalized Procrustes analysis showed a 98% consensus between SAR and clear differences between the studied regions. The canonical correlation analysis demonstrated a significant correlation between the chemical profile of SAR (r² = 0.88, P < 0.001). Therefore, the current work model provides a reliable assessment to establish rice provenance.

Rice is often grown as multiple seasons in one year, alternating between flooded and upland systems. A major constraint, introduced from the flooded system, is a plough pan that may decrease rooting depth and productivity of follow-on upland rice. Roots penetrating the plough pan under flooded rice system can leave a legacy of weaker root growth pathways. Deeper rooting rice cultivars could have a bigger impact, but no direct evidence is available. To explore whether a deep rather than a shallow rooting rice cultivar grown in a flooded cropping cycle benefited deeper root growth of follow-on rice in an upland, reduced tillage cropping cycle, a simulated flooded paddy in greenhouse was planted with deep (Black Gora) and shallow (IR64) rooting cultivars and a plant-free control. Artificial plough pans were made in between the topsoil and subsoil to form different treatments with no plough pan (0.35 MPa), soft plough pan (1.03 MPa) and hard plough pan (1.70 MPa). After harvest of this ‘first season’ rice, the soil was drained and undisturbed to simulate zero-tillage upland and planted rice cultivar BRRI Dhan 28. The overall root length density (RLD), root surface area, the numbers of root tips and branching of BRRI Dhan 28 did not vary between plough pan and no plough pan treatments. Compared with the shallow rooting rice genotype, the deep rooting rice genotype as ‘first season’ crop produced 19% greater RLD, 34% greater surface area and 29% more branching of BRRI Dhan 28 in the subsoil. In the topsoil, however, BRRI Dhan 28 had 28% greater RLD, 35% greater surface area and 43% more branching for the shallow rather than deep rooting genotype planted in the ‘first season’. The results suggested that rice cultivar selection for a paddy cycle affects root growth of a follow-on rice crop grown under no-till, with benefits to subsoil access from deep rooting cultivars and topsoil proliferation for shallow rooting cultivars.

Identification of immunity-associated leucine-rich repeat receptor-like protein kinases (LRR-RLK) is critical to elucidate the LRR-RLK mediated mechanism of plant immunity. Here, we reported the map-based cloning of a novel rice SPOTTED-LEAF 41 (OsSPL41) encoding a putative LRR-RLK protein (OsLRR-RLK41/OsSPL41) that regulated disease responses to the bacterial blight pathogen Xanthomonas oryzae pv. oryzae (Xoo). An 8-bp insertion at position 865 bp in a mutant spotted-leaf 41 (spl41) allele led to the formation of purple-brown lesions on leaves. Functional complementation by the wild type allele (OsSPL41) can rescue the mutant phenotype, and the complementary lines showed similar performance to wild type in a number of agronomic, physiological and molecular indices. OsSPL41 was constitutively expressed in all tissues tested, and OsSPL41 contains a typical transmembrane domain critical for its localization to the cell membrane. The mutant exhibited an enhanced level of resistance to Xoo in companion of markedly up-regulated expression of pathogenesis-related genes such as OsPR10a, OsPAL1 and OsNPR1, while the level of salicylic acid was significantly increased in spl41. In contrast, the over-expression lines exhibited a reduced level of H₂O₂ and were much susceptible to Xoo with down-regulated expression of pathogenesis-related genes. These results suggested that OsSPL41 might negatively regulate plant immunity through the salicylic acid signaling pathway in rice.

The main goals of rice breeding nowadays include increasing yield, improving grain quality, and promoting complete mechanized production to save labor costs. Rice grain shape, specified by three dimensions, including grain length, width and thickness, has a more precise meaning than grain size, contributing to grain appearance quality as well as grain weight and thus yield. Furthermore, the divergence of grain shape characters could be utilized in mechanical seed sorting in hybrid rice breeding systems, which has been succeeded in utilizing heterosis to achieve substantial increase in rice yield in the past decades. Several signaling pathways that regulate rice grain shape have been elucidated, including G protein signaling, ubiquitination-related pathway, mitogen-activated protein kinase signaling, phytohormone biosynthesis and signaling, microRNA process, and some other transcriptional regulatory pathways and regulators. This review summarized the recent progress on molecular mechanisms underlying rice grain shape determination and the potential of major genes in future breeding applications.