Bioengineering nitrogen acquisition in rice: can novel initiatives in rice genomics and physiology contribute to global food security?

Abstract

Rice is the most important crop species on earth, providing staple food for 70% of the world's human population. Over the past four decades, successes in classical breeding, fertilization, pest control, irrigation and expansion of arable land have massively increased global rice production, enabling crop scientists and farmers to stave off anticipated famines. If current projections for human population growth are correct, however, present rice yields will be insufficient within a few years. Rice yields will have to increase by an estimated 60% in the next 30 years, or global food security will be in danger. The classical methods of previous green revolutions alone will probably not be able to meet this challenge, without being coupled to recombinant DNA technology. Here, we focus on the promise of these modern technologies in the area of nitrogen acquisition in rice, recognizing that nitrogen deficiency compromises the realization of rice yield potential in the field more than any other single factor. We summarize rice-specific advances in four key areas of research: (1). nitrogen fixation, (2). primary nitrogen acquisition, (3). manipulations of internal nitrogen metabolism, and (4). interactions between nitrogen and photosynthesis. We develop a model for future plant breeding possibilities, pointing out the importance of coming to terms with the complex interactions among the physiological components under manipulation, in the context of ensuring proper targeting of intellectual and financial resources in this crucial area of research.

Whole-Plant Dynamic System of Nitrogen Use for Vegetative Growth and Grain Filling in Rice Plants (Oryza sativa L.) as Revealed through the Production of 350 Grains from a Germinated Seed Over 150 Days: A Review and Synthesis

“…The nitrogenous compounds in the phloem sap can act as indicators of the plant N status and constitute a signal to control root N uptake using a biochemical feedback system (Britto and Kronzucker, 2004). The phloem transport of N compounds must be fully controlled to sustain the new growth of the organs and to efficiently respond to N demands by balancing internal remobilization and exogenous root uptake: the demand of the sink organs must be adequately sensed, and certain long-distance signals must work in this sensing-signaling system.…”

Spring barley (Hordeum vulgare L.) Responses to Soil Injected Liquid Ammonium Nutrition under Different Growth Temperatures

“…This is highly possible since nitrogen form of energy uptake requirements vary greatly with ammonium assimilation consuming much lesser energy than nitrate [54,55]. The application of similar findings form the basis of rice bioengineering focused on nitrogen uptake and assimilation [41]. It is perhaps because of such factors that superior grain yields in LTR favoured CULTAN fertilization technique over conventional nitrate.…”

“…The effect of tillering ability on grain formation emphasizes its contribution to the attained yield as observed by Yan et al [37] and Li et al [38]. Alongside grain yield improvement, partial NO 3 the mechanism remains unknown [40,41,42]. Although partial NO 3 -is associated with enhancement of plant tissue NH 4 + assimilation, the pathway involved is also yet to be unravelled [43].…”

Physiological Response and Comparative Proteomic Analysis of Tobacco Seedling Roots to NH4+

“…When NH4 + as the sole nitrogen source only a few crops are suitable for growth, such as rice and conifers (Britto and Kronzucker, 2004), On the contrary, the majority of other crops display growth inhibition, reduced yield and even symptoms of toxicity, such as leaf chlorosis and a decrease in net photosynthetic rate. This is because NH4 + as the sole nitrogen source may result in plant toxicity (Kotsiras et al, 2005).…”