Wild species rice OsCERK1DY-mediated arbuscular mycorrhiza symbiosis boosts yield and nutrient use efficiency in rice breeding.

Meeting the ever-increasing food demands of a growing global population while ensuring resource and environmental sustainability presents significant challenges for agriculture worldwide. Arbuscular mycorrhizal symbiosis (AMS) has emerged as a potential solution by increasing the surface area of a plant's root system and enhancing the absorption of phosphorus, nitrogen nutrients, and water. Consequently, there is a longstanding hypothesis that rice varieties exhibiting more efficient AMS could yield higher outputs at reduced input costs, paving the way for the development of Green Super Rice (GSR). Our prior research study identified a variant, OsCERK1DY, derived from Dongxiang wild-type rice, which notably enhanced AMS efficiency in the rice cultivar "ZZ35." This variant represents a promising gene for enhancing yield and nutrient use efficiency in rice breeding. In this study, we conducted a comparative analysis of biomass, crop growth characteristics, yield attributes, and nutrient absorption at varying soil nitrogen levels in the rice cultivar "ZZ35" and its chromosome single-segment substitution line, "GJDN1." In the field, GJDN1 exhibited a higher AM colonization level in its roots compared with ZZ35. Notably, GJDN1 displayed significantly higher effective panicle numbers and seed-setting rates than ZZ35. Moreover, the yield of GJDN1 with 75% nitrogen was 14.27% greater than the maximum yield achieved using ZZ35. At equivalent nitrogen levels, GJDN1 consistently outperformed ZZ35 in chlorophyll (Chl) content, dry matter accumulation, major nutrient element accumulation, N agronomic efficiency (NAE), N recovery efficiency (NRE), and N partial factor productivity (NPFP). The performance of OsCERK1DY overexpression lines corroborated these findings. These results support a model wherein the heightened level of AMS mediated by OsCERK1DY contributes to increased nitrogen, phosphorus, and potassium accumulation. This enhancement in nutrient utilization promotes higher fertilizer efficiency, dry matter accumulation, and ultimately, rice yield. Consequently, the OsCERK1DY gene emerges as a robust candidate for improving yield, reducing fertilizer usage, and facilitating a transition towards greener, lower-carbon agriculture. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01459-8.

The Perspective of Arbuscular Mycorrhizal Symbiosis in Rice Domestication and Breeding.

In nature, symbiosis with arbuscular mycorrhizal (AM) fungi contributes to sustainable acquisition of phosphorus and other elements in over 80% of plant species; improving interactions with AM symbionts may mitigate some of the environmental problems associated with fertilizer application in grain crops such as rice. Recent developments of high-throughput genome sequencing projects of thousands of rice cultivars and the discovery of the molecular mechanisms underlying AM symbiosis suggest that interactions with AM fungi might have been an overlooked critical trait in rice domestication and breeding. In this review, we discuss genetic variation in the ability of rice to form AM symbioses and how this might have affected rice domestication. Finally, we discuss potential applications of AM symbiosis in rice breeding for more sustainable agriculture.

The expression of microRNA-197-3p regulates the proliferation of ovarian granulosa cells through CUL3 in polycystic ovarian syndrome.

MicroRNAs (miR) have been shown to exhibit marked dysregulation in polycystic ovarian syndrome (PCOS). Additionally, granulosa cell proliferation and apoptosis are important in PCOS pathogenesis. Considering this, the current study aimed at characterization of the regulatory function of miR-197-3p on the growth and proliferation of ovarian granulosa cells at the molecular level. The results showed that miR-197-3p is significantly repressed (P<0.05) in PCOS tissues and granulosa cells. Granulosa cell proliferation was significantly (P<0.05) inhibited by miR-197-3p overexpression via induction of apoptosis. In silico analysis predicted cullin 3 (CUL3) as the regulatory target of miR-197-3p, which was also confirmed by the dual luciferase reporter assay. CUL3 was overexpressed in KGN ovarian granulosa cells, and its silencing mimicked the tumor suppressive effects of miR-197-3p. Taken together, miR-197-3p exhibits a negative regulatory role in regulating granulosa ovarian cell proliferation via posttranscriptional repression of CUL3 in PCOS.

Natural variation at OsCERK1 regulates arbuscular mycorrhizal symbiosis in rice.

The symbiotic interaction between arbuscular mycorrhizal fungi (AMF) and land plants is essential for efficient nutrient acquisition and utilisation. Our understanding of key processes controlling the AMF colonisation in rice is still limited. Dongxiang wild rice (DY) exhibited a stronger colonisation with Rhizophagus irregularis than the rice cultivar Zhongzao 35 (ZZ35). Chromosome segment substitution lines were constructed and the OsCERK1 gene from DY was mapped. Transgenic plants in the japonica rice Zhonghua 11 (ZZ11) were constructed to compare root colonisation by AMF. Chromosome single-segment substitution lines containing OsCERK1DY showed higher phosphorus content and grain yield relative to ZZ35. Four amino acids substitutions were identified among the OsCERK1 haplotypes of DY, ZZ35 and ZH11 and two of these were in the second lysine-motif domain, which is essential for the differences of AMF colonisation level among rice varieties. Heterologous expression of OsCERK1DY in ZH11 significantly enhanced AMF colonisation and increased resistance against the pathogenic fungi Magnaporthe oryzae. Notably, the OsCERK1DY haplotype was absent from 4660 cultivated rice varieties. We conclude that OsCERK1 is a key gene affecting the symbiotic interaction with AMF and OsCERK1DY has the biotechnological potential to increase rice phosphorus acquisition and utilisation efficiency for sustainable agriculture.

The evolution study on Oryza rufipogon. dw by whole-genome sequencing.

The species of Oryza rufipogon. dw was first discovered at Dongxiang, Jiangxi in 1978. It is recognized as abundant in genetic resources with the characteristics of cold and insect resistance. A total of 100.15 Gb raw data was obtained from seven pair-end libraries by Illumina Hiseq4000 platform. Subsequently, a draft assembly genome of O. rufipogon. dw was generated with a final size of 422.7 Mb with a contig N50 of 15 kb and a scaffold N50 of 296.2 bb. The assembly genome size was higher than the estimated genome size (413 Mb) based on k-mer analysis. The identified repeat sequences accounted for 40.09% of the entire genome, and 32,521 protein-coding genes with an average of 4.59 exons per gene was annotated in five databases. Phylogenetic analysis using 1460 single-copy gene, O. rufipogon. dw was close with O. rufipogon by Bayes method. The wild rice species of O. rufipogon. dw divergence was estimated at ∼0.3 million years ago (Mya) from O. rufipogon, and ∼0.6 Mya from the O. sativa. The draft genome of O. rufipogon. dw provided an essential resource for its origin and evolution study.

Mapping quantitative trait loci for heat tolerance at the booting stage using chromosomal segment substitution lines in rice.

High temperature stress is a major obstacle in rice productivity. Considerable progress has been made on studying heat tolerance (HT) at different stages. However, the genetic basis of HT at the booting stage is poorly understood. In this study, we analyzed the morphological features of a heat-sensitive japonica cultivar Sasanishiki under natural high temperature stress at the booting stage. The anthers became smaller and the number, and fertility, of pollen grains were decreased significantly. As a result, there was a dramatic reduction in spikelet fertility. In contrast, the indica cultivar Habataki showed high HT and normal spikelet fertility under high temperature stress. Additonally, a set of chromosome segment substitution lines, derived from Sasanishiki and Habataki, were evaluated for HT related quantitative trait loci (QTLs) across two environments in the natural field. A total of 12 QTLs associated with HT were detected, of which, 5 were identified in two environments, and 7 in one environment. Furthermore, one of the major-effect QTLs (qHTB3-3) detected on the long arm of chromosome 3, was confirmed using overlapping substituted lines. qHTB3-3 was finally mapped between the two markers RM3525 and 3-M95, approximately 2.8 Mb apart. These findings and further gene cloning of qHTB3-3 will help us better understand the molecular control of HT in rice, and may contribute to the development of high HT rice varieties.

Mapping quantitative trait loci for heat tolerance at anthesis in rice using chromosomal segment substitution lines.

To study the genetic basis of heat tolerance at anthesis, a set of chromosome segment substitution lines (CSSLs) derived from Sasanishiki (japonica ssp. heat susceptible) and Habataki (indica spp. heat tolerant) were used for analysis across three high temperature environments. Spikelet fertility (SF), daily flowering time (DFT) and pollen shedding level (PSL) under high temperature (HT) were assessed. Eleven related QTLs were detected, of which, two QTLs qSF (ht) 2 and qSF (ht) 4.2 for spikelet fertility were identified on chromosomes 2 and 4. Four QTLs qDFT3, qDFT8, qDFT10.1 and qDFT11 for daily flowering time were detected on chromosomes 3, 8, 10 and 11. The other five QTLs qPSL (ht) 1, qPSL (ht) 4.1, qPSL (ht) 5, qPSL (ht) 7 and qPSL (ht) 10.2 on chromosomes 1, 4, 5, 7 and 10, respectively, were found had effects both on spikelet fertility and pollen shedding level. Of the 11 QTLs, 8 were overlapped with QTLs reported by others, 3 QTLs qPSL (ht) 4.1, qPSL (ht) 7 and qPSL (ht) 10.2 identified in this study were novel. The stability of qPSL (ht) 4.1 was further verified at different temperatures, which could be used to improve the pollen shedding and pollen growth on stigma for rice heat-tolerance breeding.

Characterization and fine mapping of a female fertility associated gene Ff1(t) in rice.

Female-sterile line can be used as a pollinator which has a great potential for hybrid seeds production. However, reports on female fertility are fewer than male fertility. Here, we characterized a recessive female fertility weakening mutant ff1(t) from rice. The spikelet fertility was seriously affected in the mutant. Reciprocal crosses and pollen vitality assay suggest that the decreased fertility was caused by the defective female gametophytes. Further investigation indicated that the mutant ovary development was inhibited before fertilization and failed swelling after flowering. Genetic analysis and fine mapping showed that the mutant was controlled by a single recessive gene, residing on a 16.8 kb region on the long arm of chromosome 1. The gene annotation indicated that there was only one putative gene encoding lysine decarboxylase-like protein in this region, which was allelic to LOG. Further, the sequence analysis was carried out and a substitution at the splice site of intron 2 / exon 3 was revealed in ff1(t) mutant, resulting in the change of reading frame. The finding of novel allele of LOG locus will facilitate the understanding of the mechanisms of female gametophyte development.

Automatic segmentation of echocardiography based on a morphological reconstruction algorithm.

OBJECTIVE: To improve the precision of the traditional segmentation of echocardiogram, by suppressing the influence from inherent speckle noises in medical ultrasonic images. METHOD: An automatic segmentation method based on reconstructed morphology was proposed in this paper. First, the opening and closing operations by reconstruction were imposed to the ultrasonic image. Second, the top-hat operation was used to extract the bright and/or dark features and to find out the boundaries corresponding to these features, whereby implemented the automatic segmentation. RESULT: The segmented echocardiogram had less artificial boundaries resulted from speckle noise, and could accurately be extracted the artery and ventricle. CONCLUSION: The presented method can detect both dark and bright objects accurately, and the boundary has a fine continuity. In addition, the algorithm is also applicable to the extraction of sole bright/dark features, accordingly to reduce the complexity and time needed and to improve the accuracy.