Genetic Engineering

Living organisms, including plants, have many cells. Each cell has the genetic information to dictate the way the plant looks, tastes and feels. It also determines whether plants can be infected by pathogens that cause diseases, like Huanglongbing (HLB) also known as citrus greening. The genetic information is contained in long strings of chemicals, called DNA. The DNA is organized into individual units, called genes that specify traits, like a lemon’s tart taste or a tangerine’s orange color. Sweet orange has nearly 25,000 genes specifying its traits. It turns out that the DNA “language” in in all organisms is the same, so genetic information from any organism, such as spinach, can be transferred to citrus and be used to make a new trait. Chemical scissors are used to remove the information, and chemical paste is used to place the information into the genetic information of another plant. The new information, will be passed on to the next generation. This process, termed genetic engineering, gives rise to plants with modified genetic information – termed GMO’s (genetically modified organisms) by the popular press. Scientists ‘map’ the genes of plants and insects which means they determine what each gene does and how to turn them on and off.  This mapping, combined with the ability to cut and paste genes, provides scientists with the ability to put new traits into plants and insects.

In the pages of this web site, we describe how genetic engineering tactics are being developed for citrus plants and insects in an effort to stop HLB, a currently incurable and deadly disease of citrus.

Plant engineering

In citrus, the process of genetic engineering (cutting and pasting new information into the citrus genome) has been used experimentally to protect against citrus tristeza virus (CTV) and canker diseases, provide resistance to certain insects, create dwarf varieties and afford drought and salt tolerance. More recently, efforts have focused on inserting genes from one citrus variety into another in order to lower acidity, create blood orange color, increase disease resistance and lower levels of the chemical in grapefruit that interferes with statin drugs. 

 

 

 

Psyllid engineering

Just like plants, psyllids can be genetically engineered or the viruses or endosymbionts that inhabit them can be engineered to fight the bacterium Candidatus liberibacter asiaticas (CLas) that causes huanglongbing in citrus.  A federal NIFA-CAPS grant was awarded to researchers in Florida, California, Texas and Arizona to develop a ‘Nupsyllid’.  The goal of this research is to replace the wild type Asian citrus psyllid (ACP) insect vector with a population that is unable to transmit CLas.  The genetic transformation could be delivered to the psyllid directly as a sprayable or an injection or indirectly via a virus or an endosymbiont that inhabits the psyllid.  The genetic transformation lowers the ability of bacterium to survive in the psyllid or reduces the health and development of the psyllid offspring when the nupsyllid and wild ACP mate and reproduce.