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Title: Circadian clock genes universally control key agricultural traits

item BENEDIX, CLAIRE - University Of California
item MARSHALL, CARINE - University Of California
item Harmon, Frank

Submitted to: Molecular Plant
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2015
Publication Date: 3/13/2015
Citation: Benedix, C., Marshall, C., Harmon, F.G. 2015. Circadian clock genes universally control key agricultural traits. Molecular Plant. 8(8):1135-1152.

Interpretive Summary: An endogenous molecular timer or circadian clock drives approximately 24 hour rhythms with the purpose to synchronize biological processes with daily and seasonal changes in the environment. Plants have a robust circadian clock and it is now clear this timing mechanism came about due to its positive influence on growth, development, and reproduction, among other plant activities. A newly appreciated feature of the plant circadian clock is that genes associated with the circadian clock or derived from the circadian clock have played an essential role in increasing agricultural yield. Historically, breeding efforts selected genes/loci with beneficial influence on a variety of agriculturally desirable traits such traits like height, flowering time, and seed set, without knowledge of the identity of the genes under selection. Recent identification of genes underlying such historically selected loci in pea, lentil, rice, barley, wheat, sorghum, and maize demonstrates that these genes represent alleles of circadian clock genes with altered function. This article examines three families of circadian clock genes, PSEUDO-RESPONSE REGULATOR, GIGANTEA, and the evening complex genes EARLY FLOWERING 3, EARLY FLOWERING 4 AND LUX ARRHYTHMO, that appear frequently across a broad cross section of crop plants due to their role in key agricultural traits. Furthermore, emerging areas of circadian clock control recognized in the model plant Arabidopsis thaliana are discussed to highlight exciting new avenues of experimental inquiry for crop plants and to illuminate where a focus on circadian clock genes in future plant breeding efforts could be beneficial.

Technical Abstract: Circadian clocks are endogenous timers that enable plants to synchronize biological processes with daily and seasonal environmental conditions in order to allocate resources during the most beneficial times of day and year. The circadian clock regulates a number of central plant activities, including growth, development, and reproduction, primarily through control of a substantial proportion of transcriptional activity and protein function. This article examines the role that alleles of circadian clock genes have played in domestication and improvement of crop plants. The focus here is on three groups of circadian clock genes essential to clock function in Arabidopsis thaliana: PSEUDO-RESPONSE REGULATORs, GIGANTEA, and the evening complex genes EARLY FLOWERING 3, EARLY FLOWERING 4, and LUX ARRHYTHMO. Homologous genes from each group underlie quantitative trait loci that have beneficial influences on key agricultural traits, especially flowering time but also yield, biomass, and biennial growth habit. Emerging insights into circadian clock regulation of other fundamental plant processes, including responses to abiotic and biotic stresses, are discussed to highlight promising avenues for further crop improvement.