Hai Xu

This study aimed to investigate the regulatory effects of nitrogen (N) application rate and plant density on panicle type index (PTI), yield, grain filling characteristics, and their correlations. The low-PTI rice variety DP128 (PTI = 0.15) was cultivated under field conditions at four N supply levels (0 (N₀), 140 (N₁₄₀), 200 (N₂₀₀), and 260 (N₂₆₀) kg∙ha^–1), and two plant densities (166,755 and 333,495 plants∙ha⁻¹). Results showed that N application rate, planting density, and their interactions significantly influenced yield, PTI, grain number in middle/lower secondary branches, and total grain number in lower secondary branches of rice DP128. Parameters trends were consistent over two years. Under N₂₀₀D₁₀, the total grain number in lower secondary branches was minimized, while other indices were maximized. Further analysis indicates that under high PTI conditions, the maximum grain-filling rate (G_max), mean grain-filling rate (G_mean), sucrose content, ABA/ETH ratio, and starch content in inferior grains (IGs) were all significantly elevated. Correlation analysis indicated PTI was positively correlated with yield, grain number in middle/lower secondary branches, IGs−G_max, and IGs−G_mean and negatively correlated with the total grain number in the lower secondary branches. In summary, increasing PTI can be achieved by optimizing the distribution of secondary branch grains along the panicle axis, decreasing the number of grains on the lower secondary branches, mitigating the competition for filling materials among inferior grains, improving grain-filling capacity and, ultimately, increasing rice yield.

The head rice rate, defined as the proportion of milled grains retaining at least three-quarters of their original length, has become a limiting factor that restricts the improvement of rice quality in China in recent years. Here, we characterized the role of ETHYLENE RESPONSIVE FACTOR34 (OsERF34), an APETALA2 (AP2/ERF) family TF, in the grain morphology, physiochemical properties, and processing quality of rice. Through CRISPR/Cas9-mediated knockout (Oserf34) and overexpression (OsERF34-OE) in the japonica cultivar ZH11, we demonstrate that OsERF34 exerts dose-dependent effects on grain morphology and processing traits. Oserf34 mutants exhibited significantly elevated chalkiness levels, with a 52.0% increase in percentage of grains with chalkiness(PGWC) and a 65.4% enhancement in chalkiness degree, with disordered and enlarged starch granules, reduced amylose content and skewed chain-length distribution (A/B1 chains increased but B2/B3 chains decreased), and displayed heightened starch solubility and swelling power but diminished milling resistance (shear hardness having fallen by 12.7–16.1% and compression hardness having fallen by 11.2–16.4%), culminating in doubled breakage rates and lower head rice rate (decreased by 6.7–9.0%) during processing. Strikingly, both mutants and OE lines showed analogous grain narrowing, yet the processing quality diverged. Mutants suffered structural fragility, while the OE lines enhanced mechanical robustness (compression hardness increased by 11.4–12.1%). The OsERF34-OE lines achieved 6.5–7.1% higher head rice rates. Our work positions OsERF34 as a dual-function regulator that governs grain morphology, regulating appearance and processing quality. These insights suggest that an overexpression of OsERF34 could improve processing efficiency, potentially laying a foundation for precision breeding.

Introduction: β-Mannanase is a plant cell wall remodeling enzyme involved in the breakdown of hemicellulose and plays an important role in growth by hydrolyzing the mannan-like polysaccharide, but its function in adaptation to salt stress has been less studied.Methods: Based on cloned the mannanase (MAN) gene from Mirabilis jalapa L., the study was carried out by heterologously expressing the gene in Arabidopsis thaliana, and then observing the plant phenotypes and measuring relevant physiological and biochemical indicators under 150 mM salt treatment.Results and discussion: The results indicate that MirMAN is a protein with a glycohydrolase-specific structural domain located in the cell wall. We first found that MirMAN reduced the susceptibility of transgenic Arabidopsis thaliana to high salt stress and increased the survival rate of plants by 38%. This was corroborated by the following significant changes, including the reduction in reactive oxygen species (ROS) levels, increase in antioxidant enzyme activity, accumulation of soluble sugars and increase of the expression level of RD29 in transgenic plants. We also found thatthe heterologous expression of MirMAN promoted root growth mainly by elongating the primary roots and increasing the density of lateral roots. Meanwhile, the expression of ARF7, ARF19, LBD16 and LBD29 was up-regulated in the transgenic plants, and the concentration of IAA in the roots was increased. Those results indicate that MirMAN is involved in the initiation of lateral root primordia in transgenic plants through the IAA-ARF signalling pathway. In conclusion, MirMAN improves plant salt tolerance not only by regulating ROS homeostasis, but also by promoting the development of lateral roots. Reflecting the potential of the MirMAN to promote root plastic development in adaptation to salt stress adversity.

Hybrids between different subspecies of rice Oryza sativa L. commonly show hybrid sterility. Here we show that a widely planted commercial japonica/GJ variety, DHX2, exhibited hybrid sterility when crossing with other GJ varieties. Using the high-quality genome assembly, we identified three copies of the Sc gene in DHX2, whereas Nipponbare (Nip) had only one copy of Sc. Knocking out the extra copies of Sc in DHX2 significantly improved the pollen fertility of the F₁ plant of DHX2/Nip cross. The population structure analysis revealed that a slight introgression from Basmati1 might occur in the genome of DHX2. We demonstrated that both DHX2 and Basmati1 harbored three copies of Sc. Moreover, the introgression of GS3 and BADH2/fgr from Basmati1 confers the slender and fragrance grain of DHX2. These results add to our understanding of the hybrid sterility of inter-subspecies and intra-subspecies and may provide a novel strategy for hybrid breeding.

Photosynthetica covers wide range of photosynthesis research or research including photosynthetic parameters of both experimental and theoretical nature.

Background The intensive application of inorganic nitrogen has contributed to increasing the crop yield with the risk of environmental damage. High nitrogen fertilizer requirements are a long-standing problem in japonica cultivation. Materials and methods In the present study, 200 recombinant inbred lines derived from two representative japonica varieties of Japanese and Chinese varieties, Akitakomachi and Liaogeng5, respectively, were planted under different nitrogen fertilization conditions. The relationships among nitrogen fertilization, genetic background, and important agronomic traits were surveyed through the phenotypic investigation and next-generation sequencing. Results The results showed that the yield components of Akitakomachi dramatically decreased along with the nitrogen reduction, whereas those of Liaogeng5 exhibited a slight decrease. The appearance quality and milling quality of both Akitakomachi and Liaogeng5 were improved, especially Liaogeng5. The recombinant inbred lines (RILs) showed similar trends to their parental lines. The QTLs analysis of important agronomic traits detected 17 loci, one QTL clustering located on chromosome 9 that corresponded to the plant height, panicle angle, grain number per panicle, harvest index, and taste value was identified to be synonymous with a previously reported gene, DEP1. The function of DEP1 was verified by a knock-out mutant constructed by CRISPR/Cas9. The dep1 mutant exhibited improved grain quality without severe yield penalty under nitrogen reduction conditions. Conclusion The results of the present study provide useful information for the improvement of food security by enhancing nitrogen use efficiency.

The recombinant inbred lines (RILs) population constructed by crossing between Liaojing 5 (a typical erect panicle type rice variety in Liaoning) and Akitakaomaqi (a good quality rice variety in Japan) were used as experimental materials and planted under high nitrogen and low nitrogen fertilization mode. In order to explore the possible ways to maintain stable yield while reducing the amount of nitrogen application, we investigated the stem vascular, panicle and yield traits of the RIL population and analyzed the effects of nitrogen reduction on them and their correlation. The results showed that the traits of stem vascular bundle, spike and yield of RIL population showed continuous variation under two different fertilization models, which was consistent with the genetic characteristics of quantitative traits controlled by multiple genes. The number of vascular bundles of panicle neck and penultimate internode in a stem, the area of vascular bundles of panicle neck and penultimate internode in a plant were decreased, the number of primary branches decreased, the seed setting rate of primary and secondary branches, the total seed setting rate and 1000-grain weight increased, the weight of single panicle increased, the number of panicle decreased, and the yield was decreased after nitrogen fertilizer reduction. The traits of vascular bundle in stem were closely related to the traits of panicle and yield. The traits of vascular bundle in single stem were positively correlated with the thickness of panicle neck, number of primary branches, number of secondary branches, number of panicle grains, kernel density, 1000-seed weight, and the number of panicles. The area of vascular bundle per plant was positively correlated with the number of panicles and yield. After nitrogen decrease treatment, the main characteristics of no reduction yield type in RIL populations were as follows: under the condition of low nitrogen, there was a stable differentiation of tiller and stem vascular bundle, ensuring the stable number of panicles and neck diameter; there was not significant differences in the number of big and small vascular bundles of panicle necks and penultimate internodes in a stem, the area of big vascular bundles of penultimate internodes in a stem and in a plant, and number of stems and branches. Under the condition of reducing nitrogen fertilizer, it is possible to achieve the goal of reducing nitrogen without reducing yield by selecting rice varieties with developed vascular bundles in stems and stable panicle numbers and panicle necks.

Rice not only produces grains for human beings, but also provides large amounts of lignocellulose residues, which recently highlighted as feedstock for biofuel production. Genetic modification of plant cell walls can potentially enhance biomass saccharification; however, it remains a challenge to maintain a normal growth with enhanced lodging resistance in rice. In this study, rice (Oryza sativa) mutant fc17, which harbors the substitution (F426S) at the plant-conserved region (P-CR) of cellulose synthase 4 (CESA4) protein, exhibited slightly affected plant growth and 17% higher lodging resistance compared to the wild-type. More importantly, the mutant showed a 1.68-fold enhancement in biomass saccharification efficiency. Cell wall composition analysis showed a reduction in secondary wall thickness and cellulose content, and compensatory increase in hemicelluloses and lignin content. Both X-ray diffraction and calcofluor staining demonstrated a significant reduction in cellulose crystallinity, which should be a key factor for its high saccharification. Proteomic profiling of wild-type and fc17 plants further indicated a possible mechanism by which mutation induces cellulose deposition and cell wall remodeling. These results suggest that CESA4 P-CR site mutation affects cell wall features especially cellulose structure and thereby causes enhancement in biomass digestion and lodging resistance. Therefore, CESA4 P-CR region is promising target for cell wall modification to facilitate the breeding of bioenergy rice.

Axle hypoid gear design needs axle system deformation data at mesh point under load to evaluate the contact pattern, contact pressure and bending stress of the gear pair. The system deformation data or gear deflection (GD), can be obtained through a standard test procedure defined several decades ago. The testing method has not been improved for data acquisition efficiency and reliability since then. Fundamentally it contains trade-offs that make contact pattern correlation difficult. It also cannot meet urgent axle development timing pressures and cost reduction requirements. Analysis methods have been developed in recent years to replace the testing method of GD calculation. However, published modeling methods have their own limitations, and still do not correlate well loaded contact pattern between testing and analysis. In this paper, existing approaches of GD calculation are first reviewed and compared. Then the development of a new method is outlined, which combines a general finite element software and a special gear bearing contact analysis tool in one process. The validation of the method is illustrated by comparing axle loaded contact pattern. Finally, two case studies are demonstrated. The first one shows the capability of the new method to investigate the compliance contribution of main axle components. The second one shows that during one gear rotation, GD experiences a significant variation which needs to be considered during gear design.