Rice genotype differences in tolerance of zinc-deficient soils: evidence for the importance of root-induced changes in the rhizosphere

The Supplementary Material for this article can be found online at: http://journal.frontiersin.org/article/10.3389/fpls.2015.01160Zinc (Zn) deficiency is a major constraint to rice production and Zn is also often deficient in humans with rice-based diets. Efforts to breed more Zn-efficient rice are constrained by poor understanding of the mechanisms of tolerance to deficiency. Here we assess the contributions of root growth and root Zn uptake efficiency, and we seek to explain the results in terms of specific mechanisms. We made a field experiment in a highly Zn-deficient rice soil in the Philippines with deficiency-tolerant and -sensitive genotypes, and measured growth, Zn uptake and root development. We also measured the effect of planting density. Tolerant genotypes produced more crown roots per plant and had greater uptake rates per unit root surface area; the latter was at least as important as root number to overall tolerance. Tolerant and sensitive genotypes took up more Zn per plant at greater planting densities. The greater uptake per unit root surface area, and the planting density effect can only be explained by root-induced changes in the rhizosphere, either solubilizing Zn, or neutralizing a toxin that impedes Zn uptake (possibly HCO − 3 HCO3− or Fe2+), or both. Traits for these and crown root number are potential breeding targets.This research was funded by a grant from the UK's Biotechnology and Biological Sciences Research Council (BBSRC, Grant Ref. BB/J011584/1) under the Sustainable Crop Production Research for International Development (SCPRID) programme, a joint multi-national initiative of BBSRC, the UK Government's Department for International Development (DFID) and (through a grant awarded to BBSRC) the Bill & Melinda Gates Foundation. Support to AKN in the form of a fellowship awarded by the Japan Society for the Promotion of Science (JSPS) is gratefully acknowledged

Paving the way towards future-proofing our crops

To meet the increasing global demand for food, feed, fibre and other plant-derived products, a steep increase in crop productivity is a scientifically and technically challenging imperative. The CropBooster-P project, a response to the H2020 call ‘Future proofing our plants’, is developing a roadmap for plant research to improve crops critical for the future of European agriculture by increasing crop yield, nutritional quality, value for non-food applications and sustainability. However, if we want to efficiently improve crop production in Europe and prioritize methods for crop trait improvement in the coming years, we need to take into account future socio-economic, technological and global developments, including numerous policy and socio-economic challenges and constraints. Based on a wide range of possible global trends and key uncertainties, we developed four extreme future learning scenarios that depict complementary future developments. Here, we elaborate on how the scenarios could inform and direct future plant research, and we aim to highlight the crop improvement approaches that could be the most promising or appropriate within each of these four future world scenarios. Moreover, we discuss some key plant technology options that would need to be developed further to meet the needs of multiple future learning scenarios, such as improving methods for breeding and genetic engineering. In addition, other diverse platforms of food production may offer unrealized potential, such as underutilized terrestrial and aquatic species as alternative sources of nutrition and biomass production. We demonstrate that although several methods or traits could facilitate a more efficient crop production system in some of the scenarios, others may offer great potential in all four of the future learning scenarios. Altogether, this indicates that depending on which future we are heading toward, distinct plant research fields should be given priority if we are to meet our food, feed and non-food biomass production needs in the coming decades

ERECTA receptor-kinases play a key role in the appropriate timing of seed germination under changing salinity

Appropriate timing of seed germination is crucial for the survival and propagation of plants, and for crop yield, especially in environments prone to salinity or drought. However, the exact mechanisms by which seeds perceive changes in soil conditions and integrate them to trigger germination remain elusive, especially once the seeds are non-dormant. In this study, we determined that the Arabidopsis ERECTA (ER), ERECTA-LIKE1 (ERL1), and ERECTA-LIKE2 (ERL2) leucine-rich-repeat receptor-like kinases regulate seed germination and its sensitivity to changes in salt and osmotic stress levels. Loss of ER alone, or in combination with ERL1 and/or ERL2, slows down the initiation of germination and its progression to completion, or arrests it altogether under saline conditions, until better conditions return. This function is maternally controlled via the tissues surrounding the embryo, with a primary role being played by the properties of the seed coat and its mucilage. These relate to both seed-coat expansion and subsequent differentiation and to salinity-dependent interactions between the mucilage, subtending seed coat layers and seed interior in the germinating seed. Salt-hypersensitive er105, er105 erl1.2, er105 erl2.1 and triple-mutant seeds also exhibit increased sensitivity to exogenous ABA during germination, and under salinity show an enhanced up-regulation of the germination repressors and inducers of dormancy ABA-insensitive-3, ABA-insensitive-5, DELLA-encoding RGL2, and DelayOf-Germination-1. These findings reveal a novel role of the ERECTA receptor-kinases in the sensing of conditions at the seed surface and the integration of developmental, dormancy and stress signalling pathways in seeds. They also open novel avenues for the genetic improvement of plant adaptation to changing drought and salinity patterns

Going virtual: adapting in-person interactive focus groups to the online environment

Restrictions on social interaction and travel due to the COVID-19 pandemic have affected how researchers approach fieldwork and data collection. Whilst online focus groups have received attention since the 2000s as a method for qualitative data collection, relatively little of the relevant literature appears to have made use of now ubiquitous video calling software and synchronous, interactive discussion tools. Our own experiences in organising fieldwork aimed at understanding the impact of different ‘future-proofing’ strategies for the European agri-food system during this period resulted in several methodological changes being made at short notice. We present an approach to converting in-person focus group to a virtual methodology and provide a checklist for researchers planning their own online focus groups. Our findings suggest data are comparable to in-person focus groups and factors influencing data quality during online focus groups can be safeguarded. There are several key steps, both before and during the focus groups, which can be taken to ensure the smooth running of such events. We share our reflections on this approach and provide a resource for other researchers moving to online-only data collection

Communicating about plant breeding and genome editing in plants : Assessment of European stakeholders, sources, channels and content

Genome editing helps to develop plant varieties that address future agricultural challenges such as climate change adaptation, resource efficiency and sustainable productivity. Nevertheless, associated aspects relating, besides others, to the regulation of genome editing, intellectual property rights and potential environmental and health aspects lead to fierce discussions within the European Union. In these discussions, values and moral aspects play a decisive role. To support and set the stage for an open-minded dialogue, the communication behaviour and needs of specific stakeholder groups has been analysed by means of two online surveys. The surveys considered sources and channels used for information sourcing and dissemination, conveyed content and relevant target audiences. In addition, the degree of trust of stakeholders in different information sources was assessed. Stakeholders included representatives from academia, civil society organisations (including environmental and consumer organisations), journalists, the farming community, the seed and plant breeding sector and policymakers across Europe. Our analysis suggests that, in general, a high level of trust is associated with representatives from academia, and that safety-related aspects, transparency and sustainability are considered very important topics across the different stakeholder groups. In addition, social media seem to play a subordinate role for inter-stakeholder communication but is of higher relevance for reaching out to the public

Repressive ZINC FINGER OF ARABIDOPSIS THALIANA proteins promote programmed cell death in the Arabidopsis columella root cap

Developmental programmed cell death (dPCD) controls a plethora of functions in plant growth and reproduction. In the root cap of Arabidopsis (Arabidopsis thaliana), dPCD functions to control organ size in balance with the continuous stem cell activity in the root meristem. Key regulators of root cap dPCD including SOMBRERO/ANAC033 (SMB) belong to the NAC family of transcription factors. Here we identify the C2H2 zinc finger protein ZINC FINGER OF ARABIDOPSIS THALIANA 14 ZAT14 as part of the gene regulatory network of root cap dPCD acting downstream of SMB. Similar to SMB, ZAT14 inducible misexpression leads to extensive ectopic cell death. Both the canonical EAR motif and a conserved L-box motif of ZAT14 act as transcriptional repression motifs and are required to trigger cell death. While a single zat14 mutant does not show a cell death-related phenotype, a quintuple mutant knocking out five related ZAT paralogs shows a delayed onset of dPCD execution in the columella and the adjacent lateral root cap. While ZAT14 is co-expressed with established dPCD-associated genes, it does not activate their expression. Our results suggest that ZAT14 acts as a transcriptional repressor controlling a so far uncharacterized sub-section of the dPCD gene regulatory network active in specific root cap tissues

European consumer and societal stakeholders' response to crop improvements and new plant breeding techniques

The global demand for providing nutritious, sustainable, and safe diets for a 10 billion population by 2050 while preserving affordability, reducing environmental impacts, and adapting to climate change will require accelerating the transition to sustainable agri‐food systems. A plausible way to help tackle these challenges is by developing new plant varieties that have improved crop yield, plant nutritional quality, and sustainability (or resilience) traits. However, stakeholders, consumers, and citizens' concerns and appreciation of future‐proofing crops and the acceptability of new plant breeding strategies are not well‐established. These groups are actors in the agri‐food systems, and their views, values, needs, and expectations are crucial in helping to co‐design fair, ethical, acceptable, sustainable, and socially desirable policies on new plant breeding techniques (NPBTs) and the transition to sustainable agri‐food systems. In this study, we engaged with consumer experts and societal stakeholders to consider their perceptions, expectations, and acceptability of improving crops and NPBTs for future‐proofing the agri‐food systems. Our analysis points to a need for governments to take a proactive role in regulating NPBTs, ensure openness and transparency in breeding new crop varieties, and inform consumers about the effects of these breeding programmes and the risks and benefits of the new crop varieties developed. Consumer experts and societal stakeholders considered these strategies necessary to instil confidence in society about NPBTs and accelerate the transition to sustainable agri‐food systems