Location: Plant, Soil and Nutrition ResearchTitle: Maize YABBY Genes drooping leaf1 and drooping leaf2 regulate plant architecture
|STRABLE, JOSH - Iowa State University|
|WALLACE, JASON - University Of Georgia|
|BRIGGS, SARAH - Iowa State University|
|UNGER-WALLACE, ERICA - Iowa State University|
|Buckler, Edward - Ed|
|VOLBRECHT, ERIK - Iowa State University|
Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2017
Publication Date: 7/11/2017
Citation: Strable, J., Wallace, J., Briggs, S., Unger-Wallace, E., Bradbury, P., Buckler IV, E.S., Volbrecht, E. 2017. Maize YABBY genes drooping leaf1 and drooping leaf2 affect agronomic traits by regulating leaf architecture. The Plant Cell. doi: 10.1105/tpc.16.00477.
Interpretive Summary: In maize, leaf architecture traits, such as length, width, and the angle between the leaf and stalk influence how light penetrates when plants are close together. In turn, light penetration affects photosynthetic efficiency and overall yield. This paper names and describes drooping leaf1 (drl1), a maize mutant that strongly affects leaf architecture. Plants with this mutant have leaf blades that lack a midrib, which provides stiffness to leaves, resulting in drooping leaves. Mutant leaves are shorter and narrower and have longer sheaths and internodes. This research identified the exact position of the mutant gene in the maize genome, the drl1-R allele, and found a second gene, drl2-Mo17, in the inbred line Mo17 that enhances the effect of drl1. Genome-wide association studies showed that natural variation at or near drl1 affects leaf angle, leaf width, and internode length, even though the inbreds in the study did not contain the mutant allele, drl1-R. Several naturally occurring genetic variants were shown to have a large effect on width and internode length. Further, the messenger RNA produced from drl1 was shown to accumulate in regions specific to later leaf development, which provides additional evidence for the importance of this gene in determining leaf architecture.
Technical Abstract: Leaf architectural traits, such as length, width and angle, directly influence canopy structure and light penetration, photosynthate production and overall yield. We discovered and characterized a maize (Zea mays) mutant with aberrant leaf architecture we named drooping leaf1 (drl1), as leaf blades are midribless with increased leaf angle. drl1 mutant leaves also have shorter, narrower blades, longer sheaths and longer internodes. These mutant phenotypes are drastically enhanced by a modifier locus in the Mo17 inbred. We cloned the underlying gene, the drl1-R allele, and identified its paralogous enhancer, the drl2-Mo17 allele. The genes encode the maize CRABS CLAW co-ortholog, a putative transcriptional regulator with zinc-finger and YABBY domains. Our analysis suggests natural variation in Mo17 at the drl2 locus enhances the drl1 mutant phenotypes. Genome wide association studies using maize NAM-RIL populations indicated that the drl loci reside within QTL regions for leaf angle, leaf width and internode length and identified several rare SNPs with large phenotypic effects for the latter two traits. Expression analyses demonstrate drl transcripts accumulate in lateral primordia, but not in the vegetative meristem or stem. Genetic interactions between drl mutant and natural variant alleles and the maize DE-ETIOLATED2 homolog nana plant1-R provide a pivotal connection between YABBY genes and brassinosteroids. This study illustrates the impact of drl genes on leaf architecture, a key agronomic trait.