Biological Signal Reduces Spread of Common Citrus Diseases and Increases Heat Tolerance in Citrus Plants UF researchers have identified a citrus gene that if -silenced in rootstock improves cell defenses against bacterial diseases such as the organism that causes citrus greening disease also known as Huanglongbing (HLB). Infected citrus cells barely ells detect the bacteria that cause HLB and typically fail to trigger adequate native defense systems until the bacteria have multiplied to very high levels. Citrus greening disease is the most economically costly disease threatening the world’s citrus industry; Florida alone has lost over 100000 acres of citrus trees to this disease. It is estimated that between 2006 and 2011 citrus greening cost the state of Florida over $4.5 billion in economic output and 8000 jobs. In response to this agricultural threat University of Florida researchers have identified a gene suppressor that promises to enhance plant defense responses against pathogens such as the bacterium that causes HLB. Application Gene modification for increased defense response against disease in citrus plants Technology When a pathogen infects a plant particularly inside a living cell the infected cell defends itself by triggering programmed cell death (PCD) or apoptosis. There are many triggers of apoptosis such as reactive oxygen species (ROS) which activate plant defense signaling pathways over long distances. There are also anti-apoptosis proteins which modulate plant defense responses to pathogens. By suppressing expression of these anti-apoptosis proteins PCD can occur in a more rapid manner and with augmented plant defense responses following pathogen infection. Ca. Liberibacter asiaticus (CLas) grows in the cytoplasm of living citrus phloem cells and causes citrus greening disease. CLas produces a peroxidase enzyme that dampens the ROS signaling pathway and also has evolved to eliminate the typical triggers of PCD. By employing a gene silencing strategy researchers have suppressed a gene encoding a PCD brake in citrus rootstock to enhance the defense response against CLas and thereby enhance citrus resistance to citrus greening disease.
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