Analysis at the nanoscale:addressing key problems in plant sciences with advanced analytical techniques

Arsenic (As) is a carcinogenic and toxic element. Natural contamination of drinking water with As is the main source of exposure to this element in many areas and is particularly prevalent in areas such as Bangladesh, West Bengal, and parts of China and the USA. Arsenic contamination of drinking water in Bangladesh and West Bengal has been described as the largest mass poisoning of a population in history, with millions of people affected. Rice is one of the main foods in As-epidemic areas and irrigation with As-contaminated water has resulted in rice with elevated levels of As. The European Food Safety Authority has called for As intake to be reduced. This can only be achieved with a better understanding of the pathways of As uptake and transport within rice plants and this is the aim of the first part of my project. This is a problem of genuine international significance that can only be addressed by an interdisciplinary approach.Wheat grain storage proteins are of immense importance in food processing as they form a viscoelastic network in dough trapping the carbon dioxide bubbles formed during sugar fermentation causing the dough to rise when baked. These proteins are deposited in the starchy endosperm region of the grain, which gives the white flour fraction on milling. However, the starchy endosperm is not a homogenous tissue, with clear gradients in the content and composition of starch, protein and cell wall polysaccharides. These gradients have implications for grain processing as they may allow the production of flour fractions with specific compositions and processing properties. However, they are also of fundamental interest in relation to understanding the control of endosperm development and the synthesis of the gluten proteins which determine the processing properties.This project will use NanoSIMS - state of the art high resolution secondary ion mass spectrometry - to localise As in the nodes of rice plants, the point in the stem where solutes are split into two streams with one controlling uptake to the leaves and one to the rice grain. Several transporters controlling As uptake into the grain have been identified and I will be comparing the distribution of trace amounts of As at the nodes of wild type rice plants with mutants which are missing these specific transporter genes therefore blocking the uptake of As. In the second part of my project I will use the capability of the NanoSIMS to detect isotopes to investigate the distribution of proteins in developing wheat grains. Wheat plants will be fed with compounds used for nitrogen fertilisation which have been isotopically spiked with 15N. The plant is unable to distinguish naturally occurring 14N from 15N, which has a low natural abundance, therefore its distribution in the grain can be used to directly infer mechanisms of protein synthesis. This research will primarily be undertaken at the Department of Materials at Oxford University. This is a highly collaborative project and will involve scientists working in the fields of plant physiology, environmental science, crop nutrition and cereal grain structure and composition to develop new methodologies and improve understanding of the uptake and deposition of key elements in plants. Sample preparation of biological samples for SIMS analysis is difficult and complex. The Life Sciences department at Oxford Brookes University have a lot of expertise in preparing biological materials for TEM and, as we have discovered, NanoSIMS analysis. Samples will be grown at Rothamsted Research, prepared at Oxford Brookes University and the distributions of the key elements will be determined with the NanoSIMS in the Oxford Materials department. The strong collaborative links will be used to interpret these results to make an impact to the scientific knowledge in many aspects of plant science.

Both projects outlined in this proposal will contribute new information to the scientific community and offer scientific advance in the fields of secondary ion mass spectrometry, plant nutrition and uptake mechanisms of important trace elements. The proposed research uses high resolution secondary ion mass spectrometry, traditionally a physical science technique, and applies it to 2 key biological problems showing how integrating existing techniques in the life sciences with advances in instrumentation in another discipline can provide new information in the fields of plant physiology, environmental science, crop nutrition and cereal grain structure and composition to develop new methodologies and improve understanding of the uptake and deposition of key elements in plants. The first part of my project focuses on understanding the mechanisms of uptake of As in rice plants with the aim of being able to reduce the As concentration in rice grains, a severe problem in areas such as Bangladesh. The immediate beneficiaries of this research will be those scientists who are working in this field with the research providing key data which either supports their theories or gives them key information to develop new ones. My previous research using the NanoSIMS has discovered several new and unexpected results in the subcellular distribution of metalloid elements and I am confident data from this new project will also have impact in both SIMS and plant science communities. Ultimately this research is aimed at helping the millions of people in South East Asia and other countries worldwide that are affected by As contaminated water by reducing the amount of As in rice grains and therefore improving their health and quality of life. Although a complete resolution of this problem is a long way off, this research will contribute information which could help researchers plan strategies to block As uptake before it enters the grain. The second part of my project is to investigate the deposition patterns of protein in wheat grain using isotopically spiked compounds. Again the immediate beneficiaries will be researchers in the areas of protein and wheat grain development as it will enable them to better understand these important yet poorly understood mechanisms. Nitrogen fertiliser is currently the major energy input to agriculture worldwide with major environmental as well as economic impacts, the current high yields and high protein contents required for breadmaking are not sustainable in terms of cost, energy requirement for fertiliser production and environmental footprint. Targeting applied nitrogen more effectively to optimise crop yield and quality is therefore a major goal for crop research worldwide. The bread industry is the second largest food sector with annual sales of 3 billion. Wheat grain storage proteins also play an important role in food processing ultimately controlling how well the bread rises by creating a viscoelastic network which traps carbon dioxide bubbles formed from the sugar fermentation. There is a strong gradient in protein concentration and distribution in the white bread part of the grain, the endosperm, and these gradients have implications for grain processing as they may allow the production of flour fractions with specific compositions and processing properties. The impact of the proposed research will be to provide the plant science and food processing industry with a more detailed mechanistic understanding of how to tailor growth and processing strategies for improved yield and manufacturing. I hope that my research will also benefit the general public by raising their awareness of the value of the research that is being undertaken at UK universities. This interdisciplinary project is very approachable by the general public, as I have discovered during my current research, as is work that they can relate to because these problems directly affect human lives.