Biofortification of rice with lysine using endogenous histones

Abstract

Rice is the most consumed cereal grain in the world, but deficient in the essential amino acid lysine. Therefore, people in developing countries with limited food diversity who rely on rice as their major food source may suffer from malnutrition. Biofortification of stable crops by genetic engineering provides a fast and sustainable method to solve this problem. In this study, two endogenous rice lysine-rich histone proteins, RLRH1 and RLRH2, were over-expressed in rice seeds to achieve lysine biofortification. Their protein sequences passed an allergic sequence-based homology test. Their accumulations in rice seeds were raised to a moderate level by the use of a modified rice glutelin 1 promoter with lowered expression strength to avoid the occurrence of physiological abnormalities like unfolded protein response. The expressed proteins were further targeted to protein storage vacuoles for stable storage using a glutelin 1 signal peptide. The lysine content in the transgenic rice seeds was enhanced by up to 35 %, while other essential amino acids remained balanced, meeting the nutritional standards of the World Health Organization. No obvious unfolded protein response was detected. Different degrees of chalkiness, however, were detected in the transgenic seeds, and were positively correlated with both the levels of accumulated protein and lysine enhancement. This study offered a solution to the lysine deficiency in rice, while at the same time addressing concerns about food safety and physiological abnormalities in biofortified crops.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-014-0272-z) contains supplementary material, which is available to authorized users.

HICL table can manipulate all proteins in human complete proteome

“…The HICL table was organized in 67912 rows and 28 columns and contains a header row and column for cell referencing. The numbers as showed in the header column represent the sequential numbers of the list of entries in the human complete proteome in FAST format, and the titles of columns in the header row use NO, Ala, Cys, Asp, Glu, Phe, Gly, His, Ile, Lys, Leu, Met, Asn, Pro, Gln, Arg, Ser, Thr, Val, Lysine-rich proteins have nutritive and commercial value to establish transgenic lines of cereals with high lysine content of grains [20]. It was reported that down-regulation of cysteine-rich proteins and down-regulation of methionine-rich proteins can be respectively adopted by Escherichia coli and Synechocystis to sulfur deprivation [15] .…”

Prospects for Genetic Improvement in Internal Nitrogen Use Efficiency in Rice

“…However, in many low-yielding environments in developing countries, increasing grain protein level and composition through breeding has been suggested as a means to increase the protein intake of the population, since cereals often form a large proportion of the diet [17]. With this simulation, it was demonstrated that grain protein levels could be theoretically increased to 12% with as little as a 10% reduction in current NUE agron if the NHI can be increased from 0.6 to 0.8.…”

“…However, if enhancing the protein concentration of rice grains becomes a breeding target to improve nutrition of rice consumers [17], improvement in NUE agron (and therefore NUE veg ) may be difficult unless it is also linked to more favourable grain protein composition as opposed to total grain protein levels. Similar to other cereal grains, rice grains contain albumins, globulins, glutelins and prolamins [18] with the concentration of prolamins and glutelins appearing to be linked, such that reduction in one protein fraction is compensated by an increase in the other [19].…”

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“…A large number of studies based on aspartic acid metabolism pathway have indicated that if the expression of AK and DHDPS genes was promoted or the expression of LKR/SDH genes and 13-kDa prolamine genes was inhibited, the lysine content in rice plants was significantly increased [28]; [29]. If the lysine-rich exogenous protein was specifically expressed in rice grains or the RLRH1 and RLRH2 genes were overexpressed, the lysine content in rice grains could also be significantly increased [30]; [31]. Therefore, the specific quantitative expression of the key genes in the lysine metabolism pathway can greatly enhance the lysine content in rice grains.…”