Folate fortification of rice by metabolic engineering

Abstract

Rice, the world's major staple crop, is a poor source of essential micronutrients, including folates (vitamin B9). We report folate biofortification of rice seeds achieved by overexpressing two Arabidopsis thaliana genes of the pterin and para-aminobenzoate branches of the folate biosynthetic pathway from a single locus. We obtained a maximal enhancement as high as 100 times above wild type, with 100 g of polished raw grains containing up to four times the adult daily folate requirement.

Biofortified crops to alleviate micronutrient malnutrition

“…These include recent work on tomato, which boosted folate accumulation 15-fold by tweaking a highly compartmentalized pathway [38], a feat also shown to work in rice grains [39]. Also, iron content in rice grains was doubled by the overexpression of bean ferritin [40,41].…”

Folate Polyglutamylation is Required for Rice Seed Development

“…A significant proportion of plant folates exists in a polyglutamylated form (Storozhenko et al 2007, Orsomando et al 2005, Díaz de la Garza et al 2004). This study has employed LC-MS/MS to reveal that approximately 40% of rice folate forms detected in leaf and 20% of folate in seed exists either as tetra or penta forms of the 5-CH 3 -and 5/ 10-CHO-H 4 Pte ( Table 2).…”

Genetically Modified Rice with Health Benefits as a Means to Reduce Micronutrient Malnutrition

“…Nevertheless, one could also argue that transgenic lines with a higher micronutrient content could be developed in order to tackle micronutrient deficiencies in regions with medium or low rice consumption. Storozhenko 81 , for example, reported transgenic rice lines with elevated folate levels up to 17 µg per g rice, as compared to an average of 12 µg folate per g rice.…”

“…efficacy testing, elite event selection and trait integration, is available in Dubock 94 . We further refer to several biotech studies for a detailed discussion on the technological issues regarding folate biofortification of food plants 89,95 , including rice 81 , wheat 96 and tomatoes 97 ). Third, both GM crops were subject of various consumer studies on acceptance and willingness-to-pay, health impact analyses and cost-effectiveness studies.…”

“…In the so-called 'single insertion' approach, the targeted micronutrient traits are stacked as one gene construct. A 'backcrossing' approach, where all traits are separately developed and combined through backcrossing 81,93 , is expected to be more costly, due to high regulatory and financial costs to approve all new events as single traits, as well as the time and financial costs required for the testing and approval of each event 111 . Moreover, micronutrient traits are mainly developed by different research institutes, which makes a single insertion approach the most realistic scenario.…”