Are high-lysine cereal crops still a challenge?

Abstract

The essential amino acids lysine and threonine are synthesized in higher plants via a pathway starting with aspartate that also leads to the formation of methionine and isoleucine. Lysine is one of most limiting amino acids in plants consumed by humans and livestock. Recent genetic, molecular, and biochemical evidence suggests that lysine synthesis and catabolism are regulated by complex mechanisms. Early kinetic studies utilizing mutants and transgenic plants that overaccumulate lysine have indicated that the major step for the regulation of lysine biosynthesis is at the enzyme dihydrodipicolinate synthase. Despite this tight regulation, recent strong evidence indicates that lysine catabolism is also subject to control, particularly in cereal seeds. The challenge of producing crops with a high-lysine concentration in the seeds appeared to be in sight a few years ago. However, apart from the quality protein maize lines currently commercially available, the release of high-lysine crops has not yet occurred. We are left with the question, is the production of high-lysine crops still a challenge?

Multifunctional grains for the future: genetic engineering for enhanced and novel cereal quality

“…It is synthesized in plants through the aspartate metabolic pathway, which also leads to methionine and threonine production. Various approaches to improve the lysine content in maize have been investigated (Mazur et al 1999;Ferreira et al 2005). Significant advances have been made since the isolation of the opaque-2 mutant (o2; Mertz et al 1964).…”

Efeito da adição dietética de milho de alta qualidade protéica em camundongos

“…Entretanto, ainda não se encontra um número significativo de resultados disponíveis na literatura, sendo que a maioria dos relatos, descreve parâmetros relacionados ao ganho de peso, consumo de ração, conversão alimentar e retenção de nitrogênio [10][11][12][13][14][15]18 . Contudo, a análise isolada desses parâ-metros não possibilita verificar a verdadeira ação da adição dietética de milho QPM, uma vez que os aminoácidos essenciais, presentes em níveis mais elevados nessa variedade, participam da estrutura primária de vários hormônios, neurotransmissores e proteínas do sistema imunológico que, por sua vez, estão envolvidos na regulação do metabolismo e de várias funções do organismo 19 .…”

Cloning a lysine-rich protein gene from potato (Solanum tuberosum L.) cultivar Thuong Tin and construction of the expression vector

“…Lysine is the most limiting amino acid in cereals. For the enrichment of protein quality of cereals and other crops, improvement of lysine content is essential (Ferreira et al, 2005;Sofi et al, 2009). One of the strategies to increase the essential amino acids, in particular, lysine, is to increase the protein sink by transforming plants with genes encoding stable proteins that are rich in the desired amino acid (Ufaz, Galili, 2008).…”