Using transcription of six Puccinia triticina races to identify the effective secretome during infection of wheat.
Wheat leaf rust, caused by the basidiomycete Puccinia triticina, can cause yield losses of up to 20% in wheat producing regions. During infection, the fungus forms haustoria that secrete proteins into the plant cell and effect changes in plant transcription, metabolism, and defense. It is hypothesized that new races emerge as a result of overcoming plant resistance via changes in the secreted effector proteins. To understand gene expression during infection and find genetic differences associated with races, RNA from wheat leaves infected with six different rust races, at 6 days post inoculation, was sequenced using Illumina. As P. triticina is an obligate biotroph, RNA from both the host and fungi were present and separated by alignment to the P. triticina genome and a wheat EST reference. A total of 222,571 rust contigs were assembled from 165 million reads. An examination of the resulting contigs revealed 532 predicted secreted proteins among the transcripts. Of these, 456 were found in all races. Fifteen genes were found with amino acid changes, corresponding to putative avirulence effectors potentially recognized by 11 different leaf rust resistance (Lr) genes. Twelve of the potential avirulence effectors have no homology to known genes. One gene had significant similarity to cerato-platanin, a known fungal elicitor, and another showed similarity to fungal tyrosinase, an enzyme involved in melanin synthesis. Temporal expression profiles were developed for these genes by qRT-PCR and show that the genes expression patterns were consistent between races from infection initiation to just prior to spore eruption.
USDA-ARS Hard Winter Wheat Genetics Research Unit, Department of Plant Pathology Manhattan, KS, USA.
Myron
M
Bruce
Department of Plant Pathology, Kansas State University Manhattan, KS, USA.
Kerri A
KA
Neugebauer
Département de biologie, Université de Moncton Moncton, NB, Canada.
David L
DL
Joly
Department of Plant Pathology, Kansas State University Manhattan, KS, USA.
Pierre
P
Migeon
Broad Institute of MIT and Harvard Cambridge, MA, USA.
Christina A
CA
Cuomo
Department of Plant Pathology, Kansas State University Manhattan, KS, USA.
Shichen
S
Wang
Department of Plant Pathology, Kansas State University Manhattan, KS, USA.
Eduard
E
Akhunov
Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada Summerland, BC, Canada.
Guus
G
Bakkeren
USDA-ARS Cereal Disease Laboratory, Department of Plant Pathology, University of Minnesota St. Paul, MN, USA.
James A
JA
Kolmer
USDA-ARS Hard Winter Wheat Genetics Research Unit, Department of Plant Pathology Manhattan, KS, USA.
John P
JP
Fellers
Puccinia triticina; RNA sequencing; effectors; leaf rust; secreted peptides