Researchers have successfully developed a novel method that will allows for increased disease resistance in rice without decreasing yield. A team at Duke University, working in collaboration with scientists at Huazhong Agricultural University in China, describe the findings in a paper published May 17, 2017 inside the journal Nature.
Rice is actually one of the most important staple crops, responsible for providing over one-fifth of the calories consumed by humans worldwide. Diseases caused by bacterial or fungal pathogens present a significant problem, along with also can result inside the loss of 80 percent or more of a rice crop.
Decades of research into the plant immune response have identified components that will can be used to engineer disease-resistant plants. However, their practical application to crops is actually limited due to the decreased yield associated having a constantly active defense response.
“Immunity is actually a double-edged sword, ” said study co-author Xinnian Dong, professor of biology at Duke along with also lead investigator of the study. “There is actually often a tradeoff between growth along with also defense because defense proteins are not only toxic to pathogens yet also harmful to self when overexpressed,” Dong said. “that will is actually a major challenge in engineering disease resistance for agricultural use because the ultimate goal is actually to protect the yield.”
Previous studies have focused on altering the coding sequence or upstream DNA sequence elements of a gene. These upstream DNA elements are known as promoters, along with also they act as switches that will turn on or off a gene’s expression. that will is actually the first step of a gene’s synthesis into its protein product, known as transcription.
By attaching a promoter that will gives an “on” signal to a defense gene, a plant can be engineered to be highly resistant to pathogens, though at a cost to growth along with also yield. These costs can be partially alleviated by attaching the defense gene to a “pathogen specific” promoter that will turns on inside the presence of pathogen attack.
To further alleviate the negative effects of active defense, the Dong group sought to add a different layer of control. They turned newly discovered sequence elements, called upstream open reading frames (uORFs), to help address that will problem. These sequence elements act on the intermediate of a gene, or messenger (RNA, a molecule similar to DNA) to govern its “translation” into the final protein product. A recent study by the Dong lab in an accompanying paper in Nature has identified many of these elements that will respond in a pathogen-inducible manner.
The Dong group hypothesized that will adding that will pathogen-inducible translational regulation might result in a tighter control of defense protein expression along with also minimize the lost yield associated with enhanced disease resistance.
To test that will hypothesis, the researchers started off with Arabidopsis, a flowering plant commonly used in laboratory research. They created a DNA sequence that will contains both the transcriptional along with also translational elements (uORFs) along with also fused them upstream of the potent “immune activator” gene called snc1. that will hybrid sequence was called a “transcriptional/translational cassette” along with also was inserted into Arabidopsis plants.
When plants have snc1 constitutively active, they are highly resistant to pathogens, yet have severely stunted growth. Strikingly, plants with the transcriptional/translational cassette not only have increased resistance, yet they also lacked growth defects along with also resembled healthy wild-type plants. These results show the benefits of adding translational control in engineering plants that will have increased resistance without significant costs.
The Dong group then sought to apply these findings to engineer disease-resistant rice, as the item is actually one of the earth’s most important crops. They created transgenic rice lines containing the transcriptional/translational cassette driving expression of another potent “immune activator” gene called AtNPR1. that will gene was chosen as the item has been found to confer broad spectrum pathogen resistance in a wide variety of crop species, including rice, citrus, apple along with also wheat.
The transgenic rice lines containing the transcriptional/translational cassette were infected with bacterial/fungal pathogens that will cause three major rice diseases—rice blight, leaf streak, along with also fungal blast. These showed high resistance to all three pathogens, indicating broad spectrum resistance could be achieved. Importantly, when grown inside the field, their yield—both in terms of grain quantity along with also quality per plant—was almost unaffected. These results indicate a great potential for agricultural applications.
that will strategy is actually the first known use of adding translational control for the engineering of disease-resistant crops with minimal yield costs. the item has many advantages, as the item is actually broadly applicable to a variety of crop species against many pathogens. Since that will strategy involves activating the plants’ endogenous defenses, the item may also reduce the use of pesticides on crops along with also hence protect the environment.
Additionally, these findings may be broadly applicable to different systems as well. These upstream elements (uORFs) are widely present in organisms coming from yeast to humans, with nearly half of all human transcripts containing them. “The great potential in using these elements in controlling protein translation during specific biological processes has yet to be realized,” Dong said.
fresh rice fights off drought
Guoyong Xu et al. uORF-mediated translation allows engineered plant disease resistance without fitness costs, Nature (2017). DOI: 10.1038/nature22372