Effect of temperature on RNA silencing of citrus psorosis virus

VELÁZQUEZ, K; RENOVELL, A; COMELLAS, M.; GARCIA ML; NAVARRO, L; PINA. J.A.; MORENO P; GUERRI J

PLANT PATHOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2009

0032-0862

For Pee Citrus  psorosis  virus  (CPsV),  genus Ophiovirus,  causes  a  bark  scaling  disease  of citrus.  CPsV  virions  are  kinked  filaments  with  three  negative-stranded  RNA molecules  (vRNA)  and  a  48-kDa  coat  protein.  We  examined  the  effect  of temperature  on  symptom  expression,  virus  accumulation  and  RNA  silencing  in sweet  orange  seedlings  (Citrus  sinensis  (L.)  Osb.)  graft-inoculated  with  three different  CPsV  isolates  and  grown  in  a  greenhouse  at  26/18ºC  or  at  32/26ºC (day/night). Most  plants  kept  in  the  cooler  greenhouse  showed  in  the  first  flush  a shock reaction with shoot necrosis, and  then moderate  to  intense chlorotic flecking and  spotting  in young  leaves, whereas plants  incubated at 32/26ºC did not  exhibit eer Reviewshoot  necrosis  and  young  leaf  symptoms  were  milder.  Virus  titre  estimated  by ELISA  and  by  northern  and  dot  blot  hybridisation  paralleled  symptom  intensity, with  significantly  higher  virus  accumulation  in  plants  incubated  at  26/18ºC.  The amount of CPsV-derived small RNAs (CPsV-sRNAs) slightly increased at 32/26ºC, with  the  ratio CPsV-sRNA/vRNA being higher  at 32/26ºC  than at 26/18ºC. These results  suggest  that  i) CPsV  infection  induces RNA  silencing  in  citrus  plants,  ii) symptom  intensity  is  associated  with  virus  accumulation,  and  iii)  temperature increase enhances  the RNA  silencing  response of citrus plants and decreases virus accumulation