A leaf-emanated signal orchestrates grain size and number in response to maternal resources.

In plants, variations in seed size and number are outcomes of different reproductive strategies. Both traits are often environmentally influenced, suggesting that a mechanism exists to coordinate these phenotypes in response to available maternal resources. Yet, how maternal resources are sensed and influence seed size and number is largely unknown. Here, we report a mechanism that senses maternal resources and coordinates grain size and number in the wild rice Oryza rufipogon, a wild progenitor of Asian cultivated rice. We showed that FT-like 9 (FTL9) regulates both grain size and number and that maternal photosynthetic assimilates induce FTL9 expression in leaves to act as a long-range signal that increases grain number and reduces size. Our findings highlight a strategy that benefits wild plants to survive in a fluctuating environment. In this strategy, when maternal resources are sufficient, wild plants increase their offspring number while preventing an increase in offspring size by the action of FTL9, which helps expand their habitats. In addition, we found that a loss-of-function allele (ftl9) is prevalent among wild and cultivated populations, offering a new scenario in the history of rice domestication.

Control of Plant Cell Growth and Proliferation by MO25A, a Conserved Major Component of the Mammalian Sterile 20-Like Kinase Pathway.

The precise control of cell growth and proliferation underpins the development of plants and animals. These factors affect the development and size of organs and the body. In plants, the growth and proliferation of cells are regulated by environmental stimuli and intrinsic signaling, allowing different cell types to have specific growth and proliferation characteristics. An increasing number of factors that control cell division and growth have been identified. However, the mechanisms underlying cell type-specific cell growth and proliferation characteristics in the normal developmental context are poorly understood. Here, we analyzed the rice mutant osmo25a1, which is defective in the progression of embryogenesis. The osmo25a1 mutant embryo developed incomplete embryonic organs, such as the shoot and root apical meristems. It showed a delayed progression of embryogenesis, associated with the reduced mitotic activity. The causal gene of this mutation encodes a member of the Mouse protein-25A (MO25A) family of proteins that have pivotal functions in a signaling pathway that governs cell proliferation and polarity in animals, yeasts and filamentous fungi. To elucidate the function of plant MO25A at the cellular level, we performed a functional analysis of MO25A in the moss Physcomitrium patens. Physcomitrium patens MO25A was uniformly distributed in the cytoplasm and functioned in cell tip growth and the initiation of cell division in stem cells. Overall, we demonstrated that MO25A proteins are conserved factors that control cell proliferation and growth.

High-resolution spatiotemporal transcriptome analyses during cellularization of rice endosperm unveil the earliest gene regulation critical for aleurone and starchy endosperm cell fate specification.

The major tissues of the cereal endosperm are the starchy endosperm (SE) in the inner and the aleurone layer (AL) at the outer periphery. The fates of the cells that comprise these tissues are determined according to positional information; however, our understanding of the underlying molecular mechanisms remains limited. Here, we conducted a high-resolution spatiotemporal analysis of the rice endosperm transcriptome during early cellularization. In rice, endosperm cellularization proceeds in a concentric pattern from a primary alveolus cell layer, such that developmental progression can be defined by the number of cell layers. Using laser-capture microdissection to obtain precise tissue sections, transcriptomic changes were followed through five histologically defined stages of cellularization from the syncytial to 3-cell layer (3 L) stage. In addition, transcriptomes were compared between the inner and the outermost peripheral cell layers. Large differences in the transcriptomes between stages and between the inner and the peripheral cells were found. SE attributes were expressed at the alveolus-cell-layer stage but were preferentially activated in the inner cell layers that resulted from periclinal division of the alveolus cell layer. Similarly, AL attributes started to be expressed only after the 2 L stage and were localized to the outermost peripheral cell layer. These results indicate that the first periclinal division of the alveolus cell layer is asymmetric at the transcriptome level, and that the cell-fate-specifying positional cues and their perception system are already operating before the first periclinal division. Several genes related to epidermal identity (i.e., type IV homeodomain-leucine zipper genes and wax biosynthetic genes) were also found to be expressed at the syncytial stage, but their expression was localized to the outermost peripheral cell layer from the 2 L stage onward. We believe that our findings significantly enhance our knowledge of the mechanisms underlying cell fate specification in rice endosperm.

Collection, preservation and distribution of Oryza genetic resources by the National Bioresource Project RICE (NBRP-RICE).

Biological resources are the basic infrastructure of bioscience research. Rice (Oryza sativa L.) is a good experimental model for research in cereal crops and monocots and includes important genetic materials used in breeding. The availability of genetic materials, including mutants, is important for rice research. In addition, Oryza species are attractive to researchers for both finding useful genes for breeding and for understanding the mechanism of genome evolution that enables wild plants to adapt to their own habitats. NBRP-RICE contributes to rice research by promoting the usage of genetic materials, especially wild Oryza accessions and mutant lines. Our activity includes collection, preservation and distribution of those materials and the provision of basic information on them, such as morphological and physiological traits and genomic information. In this review paper, we introduce the activities of NBRP-RICE and our database, Oryzabase, which facilitates the access to NBRP-RICE resources and their genomic sequences as well as the current situation of wild Oryza genome sequencing efforts by NBRP-RICE and other institutes.

A genome-wide association study using a Vietnamese landrace panel of rice (Oryza sativa) reveals new QTLs controlling panicle morphological traits.

CONTEXT: Yield improvement is an important issue for rice breeding. Panicle architecture is one of the key components of rice yield and exhibits a large diversity. To identify the morphological and genetic determinants of panicle architecture, we performed a detailed phenotypic analysis and a genome-wide association study (GWAS) using an original panel of Vietnamese landraces. RESULTS: Using a newly developed image analysis tool, morphological traits of the panicles were scored over two years: rachis length; primary, secondary and tertiary branch number; average length of primary and secondary branches; average length of internode on rachis and primary branch. We observed a high contribution of spikelet number and secondary branch number per panicle to the overall phenotypic diversity in the dataset. Twenty-nine stable QTLs associated with seven traits were detected through GWAS over the two years. Some of these QTLs were associated with genes already implicated in panicle development. Importantly, the present study revealed the existence of new QTLs associated with the spikelet number, secondary branch number and primary branch number traits. CONCLUSIONS: Our phenotypic analysis of panicle architecture variation suggests that with the panel of samples used, morphological diversity depends largely on the balance between indeterminate vs. determinate axillary meristem fate on primary branches, supporting the notion of differences in axillary meristem fate between rachis and primary branches. Our genome-wide association study led to the identification of numerous genomic sites covering all the traits studied and will be of interest for breeding programs aimed at improving yield. The new QTLs detected in this study provide a basis for the identification of new genes controlling panicle development and yield in rice.

Employing fruit juices to hydrolyze edible bird's nest and enhance the antioxidant, anti-tyrosinase, and wound-healing activities of the hydrolysates.

Enzymatic hydrolysis of edible bird's nest (EBN) has attracted great interest in both scientific and commercial fields due to the enhancement of solubility and nutraceutical values. The present study attempted to investigate the hydrolysis of EBN with papaya (Carica papaya L.), pineapple (Ananas comosus (L.) Merr.), and cantaloupe (Cucumis melo L.) juices as well as two commercial enzymes papain and bromelain. Our analysis revealed that EBN hydrolysis with pineapple juice and bromelain produced a degree of hydrolysis (DH) value of approximately 27 % while it was about 25 % for the hydrolysis with cantaloupe juice and 22 % for the hydrolysis with papaya juice and papain after 4 h of treatment. When EBN was digested by fruit juices and enzymes, the protein solubility and free sialic acid content were increased and the highest values were achieved for EBN hydrolysis with pineapple juice and bromelain (estimately 11 mg/mL of soluble protein and 18 g/kg of free sialic acid). The ABTS•+-scavenging, •OH-scavenging, and anti-tyrosinase capacities were higher in the EBN hydrolysates by papaya juice (IC50 of 0.034, 0.108, and 0.419 mg/mL, respectively), pineapple juice (IC50 of 0.025, 0.045, and 0.190 mg/mL, respectively), and cantaloupe juice (IC50 of 0.031 mg/mL, 0.056, and 0.339 mg/mL, respectively) than in the hydrolysates by unhydrolyzed EBN (IC50 of 0.094, 0.366, and 1.611 mg/mL, respectively). An improvement in ABTS•+-scavenging, •OH-scavenging, and anti-tyrosinase abilities was also observed for the hydrolysates by papain (IC50 of 0.041, 0.129, and 0.417 mg/mL, respectively) and bromelain (IC50 of 0.025, 0.069, and 0.336 mg/mL, respectively) but in a lesser extent as compared to the hydrolysates by respective papaya and pineapple juices. Noticeably, the EBN hydrolysates by fruit juices remarkably enhanced the wound closure in human fibroblasts by about 1.4-1.8 times after 24 h of treatment whereas this property was insignificant in the hydrolysates by enzymes. As papaya, pineapple, and cantaloupe juices are easily obtainable and have pleasant flavors, our results provide a possible method to hydrolyze EBN and apply the resultant hydrolysates in functional food products.

Genome Wide Association Study Pinpoints Key Agronomic QTLs in African Rice Oryza glaberrima.

BACKGROUND: African rice, Oryza glaberrima, is an invaluable resource for rice cultivation and for the improvement of biotic and abiotic resistance properties. Since its domestication in the inner Niger delta ca. 2500 years BP, African rice has colonized a variety of ecologically and climatically diverse regions. However, little is known about the genetic basis of quantitative traits and adaptive variation of agricultural interest for this species. RESULTS: Using a reference set of 163 fully re-sequenced accessions, we report the results of a Genome Wide Association Study carried out for African rice. We investigated a diverse panel of traits, including flowering date, panicle architecture and resistance to Rice yellow mottle virus. For this, we devised a pipeline using complementary statistical association methods. First, using flowering time as a target trait, we found several association peaks, one of which co-localised with a well described gene in the Asian rice flowering pathway, OsGi, and identified new genomic regions that would deserve more study. Then we applied our pipeline to panicle- and resistance-related traits, highlighting some interesting genomic regions and candidate genes. Lastly, using a high-resolution climate database, we performed an association analysis based on climatic variables, searching for genomic regions that might be involved in adaptation to climatic variations. CONCLUSION: Our results collectively provide insights into the extent to which adaptive variation is governed by sequence diversity within the O. glaberrima genome, paving the way for in-depth studies of the genetic basis of traits of interest that might be useful to the rice breeding community.

Agrobacterium-Mediated Genetic Transformation of Wild Oryza Species Using Immature Embryos.

Genetic transformation is one of the most important technologies for revealing or modulating gene function. It is used widely in both functional genomics and molecular breeding of rice. Demands on its use in wild Oryza species is increasing because of their high genetic diversity. Given the difficulties in genetic crosses between distantly related species, genetic transformation offers a way to alter or transfer genetic traits in wild rice accessions. However, transformation of wild Oryza accessions by conventional methods using calli induced from scutellum tissue of embryos in mature seeds often fails. Here, we report methods using immature embryos for the genetic transformation of a broad range of Oryza species. First, we investigated the ability of callus induction and regeneration from immature embryos of 192 accessions in 20 species under several culture conditions. We regenerated plants from immature embryos of 90 accessions in 16 species. Next, we optimized the conditions of Agrobacterium infection using a vector carrying the GFP gene driven by the maize ubiquitin promoter. GFP signals were observed in 51 accessions in 11 species. We analyzed the growth and seed set of transgenic plants of O. barthii, O. glumaepatula, O. rufipogon, and O. brachyantha. The plants grew to maturity and set seeds normally. Southern blot analyses using DNA from T0 plants showed that all GFP plants were derived from independent transformation events. We confirmed that the T-DNAs were transmitted to the next generation through the segregation of GFP signals in the T1 generation. These results show that many Oryza species can be transformed by using modified immature-embryo methods. This will accelerate the use of wild Oryza accessions in molecular genetic analyses and molecular breeding.