Root systems consist of different root types (RTs) with distinct developmental and functional characteristics. RTs may be individually reprogrammed in response to their microenvironment to maximize adaptive plasticity. Molecular understanding of such specific remodeling-although crucial for crop improvement-is limited. Here, RT-specific transcriptomes of adult rice crown, large and fine lateral roots were assessed, revealing molecular evidence for functional diversity among individual RTs. Of the three rice RTs, crown roots displayed a significant enrichment of transcripts associated with phytohormones and secondary cell wall (SCW) metabolism, whereas lateral RTs showed a greater accumulation of transcripts related to mineral transport. In nature, arbuscular mycorrhizal (AM) symbiosis represents the default state of most root systems and is known to modify root system architecture. Rice RTs become heterogeneously colonized by AM fungi, with large laterals preferentially entering into the association. However, RT-specific transcriptional responses to AM symbiosis were quantitatively most pronounced for crown roots despite their modest physical engagement in the interaction. Furthermore, colonized crown roots adopted an expression profile more related to mycorrhizal large lateral than to noncolonized crown roots, suggesting a fundamental reprogramming of crown root character. Among these changes, a significant reduction in SCW transcripts was observed that was correlated with an alteration of SCW composition as determined by mass spectrometry. The combined change in SCW, hormone-and transport-related transcript profiles across the RTs indicates a previously overlooked switch of functional relationships among RTs during AM symbiosis, with a potential impact on root system architecture and functioning.rice | root system | arbuscular mycorrhizal symbiosis | transcriptome | secondary cell wall

Purple acid phosphatases (PAPs) play an important role in plant phosphorus nutrition, both by liberating phosphorus from organic sources in the soil and by modulating distribution within the plant throughout growth and development. Furthermore, members of the PAP protein family have been implicated in a broader role in plant mineral homeostasis, stress responses and development. We have identified 33 candidate PAP encoding gene models in the maize (Zea mays ssp. mays var. B73) reference genome. The maize Pap family includes a clear single-copy ortholog of the Arabidopsis gene AtPAP26, shown previously to encode both major intracellular and secreted acid phosphatase activities. Certain groups of PAPs present in Arabidopsis, however, are absent in maize, while the maize family contains a number of expansions, including a distinct radiation not present in Arabidopsis. Analysis of RNA-sequencing based transcriptome data revealed accumulation of maize Pap transcripts in multiple plant tissues at multiple stages of development, and increased accumulation of specific transcripts under low phosphorus availability. These data suggest the maize PAP family as a whole to have broad significance throughout the plant life cycle, while highlighting potential functional specialization of individual family members.

Meeting the challenge of food and nutritional security requires ongoing innovation, particularly in managing dietary nutritional information for pre-breeding analysis, selection, and cultivation of specific food crops and cultivars. At present, the ability to compare the relative nutritional value of crops is limited, with data management systems for most crops often inconsistent and poorly integrated. Here, we review generic efforts to standardize the description and management of crop trait data and discuss several issues currently constraining their exchange and comparison, with a focus on knowledge representation related to dietary nutrition. These issues include lack of consistency within or between crop specific databases, as well as limited data standardization and interoperability. At present, the use of common descriptors or controlled vocabularies between crops is fragmentary, with only partial implementation or uptake of formal ontologies, particularly for dietary nutritional composition. Although development of the existing Crop Ontology (CO) system has improved data sharing and reuse, it represents only a limited set of trait classes and crops. We identify the need for more robust and generic ontologies, particularly those that may address crop contributions to human dietary nutrition. We propose development of a Crop Dietary Nutrition Ontology (CDNO) as a robust structured controlled vocabulary for dietary nutritional composition and function, and provide examples of specific use cases and different end users who would benefit from using CDNO terms in their database searches. This development is likely to transform the way in which crops may be compared in terms of optimal dietary nutritional values.

BACKGROUND: Food security is recognized as a major global challenge, yet human food-chain systems are inherently not geared towards nutrition, with decisions on crop and cultivar choice not informed by dietary composition. Currently, food compositional tables and databases (FCT/FCDB) are the primary information sources for decisions relating to dietary intake. However, these only present single mean values representing major components. Establishment of a systematic controlled vocabulary to fill this gap requires representation of a more complex set of semantic relationships between terms used to describe nutritional composition and dietary function. RESULTS: We carried out a survey of 11 FCT/FCDB and 177 peer-reviewed papers describing variation in nutritional composition and dietary function for food crops to identify a comprehensive set of terms to construct a controlled vocabulary. We used this information to generate a Crop Dietary Nutrition Data Framework (CDN-DF), which incorporates controlled vocabularies systematically organized into major classes representing nutritional components and dietary functions. We demonstrate the value of the CDN-DF for comparison of equivalent components between crop species or cultivars, for identifying data gaps andpotential for formal meta-analysis. The CDN-DF also enabled us to explore relationships between nutritional components and the functional attributes of food. CONCLUSION: We have generated a structured crop dietary nutrition data framework, which is generally applicable to the collation and comparison of data relevant to crop researchers, breeders, and other stakeholders, and will facilitate dialogue with nutritionists. It is currently guiding the establishment of a more robust formal ontology.

Informed policy and decision-making for food systems, nutritional security, and global health would benefit from standardization and comparison of food composition data, spanning production to consumption. To address this challenge, we present a formal controlled vocabulary of terms, definitions, and relationships within the Compositional Dietary Nutrition Ontology (CDNO, www.cdno.info) that enables description of nutritional attributes for material entities contributing to the human diet. We demonstrate how ongoing community development of CDNO classes can harmonize trans-disciplinary approaches for describing nutritional components from food production to diet.