Gene (in rice) that confers broad-spectrum resistance to a class of herbicides

Rice (Oryza sativa L.) is a staple food for almost half of the world’s population of 7.53 billion. Genetic variation revealed by characterization of genomes of the genus Oryza — including domesticated and wild species — has allowed identification of genes useful for crop breeding. Efficient crop production in large-scale farming depends on weed control with herbicides. It is well known, however, that long-term use of the same herbicide, or class of herbicide, can lead to the appearance of resistant weeds.

New combinations of herbicides and herbicide-resistance genes are therefore needed for continued success at crop breeding.

The β-triketone herbicides (bTHs) are 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors, and are applied widely in agriculture. The bTH, benzobicyclon (BBC), (see Figure 1A of attached paper), developed for weed control in rice paddy fields, shows effectiveness against paddy weeds resistant to other types of herbicide, including sulfonylureas. However, some high-yield rice varieties are susceptible to BBC (see Figure 1B & 1C of attached paper), and the gene(s) responsible for BBC sensitivity had not yet been identified. Authors therefore set out to identify the rice gene that determines BBC resistance vs sensitivity.

Authors [see attached article] identified the rice gene, HIS1 (HPPD INHIBITOR SENSITIVE-1), that confers resistance to BBC and other bTHs. Authors determined that HIS1 encodes an enzyme — Fe(II)/2-oxoglutarate–dependent oxygenase — that detoxifies bTHs by catalyzing their hydroxylation. Genealogy analysis revealed that BBC-sensitive rice variants inherited a dysfunctional his1 allele from an indica rice variety. Forced expression of the HIS1 gene in Arabidopsis thaliana [a small flowering plant, easy to grow and clone and therefore widely used as a model organism in plant biology labs; it is a member of the mustard (Brassicaceae) family that includes cabbage and radish] conferred resistance not only to BBC but also to four additional bTHs. The HIS1 gene may therefore prove useful for breeding herbicide-resistant crops. 😊

Science 26 July 2019; 365: 393-396

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