Knocking down expression of the auxin-amidohydrolase IAR3 altersdefense responses in Solanaceae family plants

D' IPPOLITO, S.; CASALONGUÉ, CLAUDIA; MATTHIEU JOOSTEN; RADOMIRA VANKOVA; FIOL, DIEGO

PLANT SCIENCE

ELSEVIER IRELAND LTD

Lugar: Amsterdam; Año: 2016 vol. 253 p. 31 - 39

0168-9452

In plants, indole-3-acetic acid (IAA) amido hydrolases (AHs) participate in auxin homeostasis by releas-ing free IAA from IAA-amino acid conjugates. We investigated the role of IAR3, a member of the IAAamido hydrolase family, in the response of Solanaceous plants challenged by biotrophic and hemi-biotrophic pathogens. By means of genome inspection and phylogenic analysis we firstly identifiedIAA-AH sequences and putative IAR3 orthologs in Nicotiana benthamiana, tomato and potato. We eval-uated the involvement of IAR3 genes in defense responses by using virus-induced gene silencing. Weobserved that N. benthamiana and tomato plants with knocked-down expression of IAR3 genes containedlower levels of free IAA and presented altered responses to pathogen attack, including enhanced basaldefenses and higher tolerance to infection in susceptible plants. We showed that IAR3 genes are con-sistently up-regulated in N. benthamiana and tomato upon inoculation with Phytophthora infestans andCladosporium fulvum respectively. However, IAR3 expression decreased significantly when hypersensi-tive response was triggered in transgenic tomato plants coexpressing the Cf-4 resistance gene and theavirulence factor Avr4. Altogether, our results indicate that changes in IAR3 expression lead to alterationin auxin homeostasis that ultimately affects plant defense responses.