Simple sequence repeats provide a substrate for phenotypic variation in the Neurospora crassa circadian clock.
BACKGROUND
WHITE COLLAR-1 (WC-1) mediates interactions between the circadian clock and the environment by acting as both a core clock component and as a blue light photoreceptor in Neurospora crassa. Loss of the amino-terminal polyglutamine (NpolyQ) domain in WC-1 results in an arrhythmic circadian clock; this data is consistent with this simple sequence repeat (SSR) being essential for clock function.


RESULTS
Since SSRs are often polymorphic in length across natural populations, we reasoned that investigating natural variation of the WC-1 NpolyQ may provide insight into its role in the circadian clock. We observed significant phenotypic variation in the period, phase and temperature compensation of circadian regulated asexual conidiation across 143 N. crassa accessions. In addition to the NpolyQ, we identified two other simple sequence repeats in WC-1. The sizes of all three WC-1 SSRs correlated with polymorphisms in other clock genes, latitude and circadian period length. Furthermore, in a cross between two N. crassa accessions, the WC-1 NpolyQ co-segregated with period length.


CONCLUSIONS
Natural variation of the WC-1 NpolyQ suggests a mechanism by which period length can be varied and selected for by the local environment that does not deleteriously affect WC-1 activity. Understanding natural variation in the N.crassa circadian clock will facilitate an understanding of how fungi exploit their environments.
Michael
Todd P
TP
Department of Plant Pathology, Cornell University, Ithaca, New York, United States of America; Plant Biology Laboratory, Salk Institute, La Jolla, California, United States of America.
Park
Sohyun
S
Kim
Tae-Sung
TS
Booth
Jim
J
Byer
Amanda
A
Sun
Qi
Q
Chory
Joanne
J
Lee
Kwangwon
K
D002940:Circadian Rhythm; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D014644:Genetic Variation; D018895:Microsatellite Repeats / Q000235:genetics*; D009492:Neurospora crassa / Q000235:genetics* / Q000502:physiology*; D010641:Phenotype
D005656:Fungal Proteins