Signaling from maize organ primordia via FASCIATED EAR3 regulates stem cell proliferation and yield traits.

Shoot apical meristems are stem cell niches that balance proliferation with the incorporation of daughter cells into organ primordia. This balance is maintained by CLAVATA-WUSCHEL feedback signaling between the stem cells at the tip of the meristem and the underlying organizing center. Signals that provide feedback from organ primordia to control the stem cell niche in plants have also been hypothesized, but their identities are unknown. Here we report FASCIATED EAR3 (FEA3), a leucine-rich-repeat receptor that functions in stem cell control and responds to a CLAVATA3/ESR-related (CLE) peptide expressed in organ primordia. We modeled our results to propose a regulatory system that transmits signals from differentiating cells in organ primordia back to the stem cell niche and that appears to function broadly in the plant kingdom. Furthermore, we demonstrate an application of this new signaling feedback, by showing that weak alleles of fea3 enhance hybrid maize yield traits.The fea3-0 allele was kindly provided by Victor Shcherbak, Krasnodar Res. Inst. Agric., Russia. We acknowledge funding from a collaborative agreement with Dupont Pioneer, and from NSF Plant Genome Research Program grant # IOS-1238202 and MCB-1027445, and with the support of the Gatsby Charitable Foundation (GAT3395/PR4) and Swedish Research Council (VR2013-4632) to HJ, and "Next-Generation BioGreen 21 Program (SSAC, Project No. PJ01137901)" Rural Development Administration, Republic of Korea. We also thank Ulises Hernandez for assistance with cloning, Amandine Masson for assistance with peptide assays, and members of the Jackson lab for comments on the manuscript.This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Nature Publishing Group

The Impact of Fasciation on Maize Inflorescence Architecture

How functional genetics research can be applied to improving crop yields is a timely challenge. One of the most direct methods is to produce larger inflorescences with higher productivity, which should be accompanied by a balance between stem cell proliferation and lateral organ initiation in meristems. Unbalanced proliferation of stem cells causes the fasciated inflorescences, which reflect the abnormal proliferation of meristems, derived from the Latin word ‘fascis’, meaning ‘bundle’. Maize, a model system for grain crops, has shown tremendous yield improvements through the mysterious transformation of the female inflorescence during domestication. In this review, we focus on maize inflorescence architecture and highlight the patterns of fasciation, including recent progress

Transposon Ac/Ds-induced chromosomal rearrangements at the rice OsRLG5 locus

Previous studies have shown that pairs of closely-linked Ac/Ds transposable elements can induce various chromosomal rearrangements in plant genomes. To study chromosomal rearrangements in rice, we isolated a line (OsRLG5-161) that contains two inversely-oriented Ds insertions in OsRLG5 (Oryza sativa Receptor like kinase Gene 5). Among approximately 300 plants regenerated from OsRLG5-161 heterozygous seeds, 107 contained rearrangements including deletions, duplications and inversions of various sizes. Most rearrangements were induced by previously identified alternative transposition mechanism. Furthermore, we also detected a new class of rearrangements that contain juxtaposed inversions and deletions on the same chromosome. We propose that these novel alleles were generated by a previously unreported type of alternative transposition reactions involving the 5′ and 3′ termini of two inversely-oriented Ds elements located on the same chromatid. Finally, 11% of rearrangements contained inversions resulting from homologous recombination between the two inverted Ds elements in OsRLG5-161. The high frequency inheritance and great variety of rearrangements obtained suggests that the rice regeneration system results in a burst of transposition activity and a relaxation of the controls which normally limit the transposition competence of individual Ds termini. Together, these results demonstrate a greatly enlarged potential of the Ac/Ds system for plant chromosome engineering

Brassinosteroid homeostasis via coordinate regulation of signaling and synthetic pathways

A widely accepted regulatory mechanism in maintaining hormone homeostasis involves negative or positive feedback control of biosynthetic genes through signal transduction pathways triggered by hormones. For brassinosteroid (BR) homeostasis, the antagonistic relationship between signaling and biosynthetic pathways has been well characterized. We have identified a transcriptional regulator, RAV-Like1, which activates both a BR receptor gene (BRI1) and BR synthetic genes (D2, D11 and BRD1). RAVL1 possesses a B3 DNA binding domain that exhibits differential affinity for E-box elements in the promoters of BRI1, D2, D11 and BRD1. Semi-dwarfism and BR-insensitive phenotypes are exhibited by ravl1 mutants. Genetic studies have demonstrated that expression alteration of BRI1 and BR synthetic genes by RAVL1 results in changes in BR sensitivity. BZR1 is a negative regulator involved in BR feedback mechanisms. To examine the relationship between RAVL1 and BZR1, expression of the common target gene BRD1 was examined using a transient transcription assay. The suppression of BRD1 by BZR1 is epistatic to activation by RAVL1. More importantly, RAVL1 is not subject to BR feedback regulation. Taken together, this data indicates that RAVL1 is involved in maintaining the basal activity of BRI1 and BR synthetic genes, which ensures that the basal levels of the hormone are produced. This study elucidated the RAVL1-mediated basal activation system which, in cooperation with negative feedback mechanisms, maintains BR homeostasis in higher plants

The maize heterotrimeric G protein β subunit controls shoot meristem development and immune responses

Heterotrimeric G proteins are important transducers of receptor signaling, functioning in plants with CLAVATA receptors in controlling shoot meristem size and with pathogen-associated molecular pattern receptors in basal immunity. However, whether specific members of the heterotrimeric complex potentiate cross-talk between development and defense, and the extent to which these functions are conserved across species, have not yet been addressed. Here we used CRISPR/Cas9 to knock out the maize G protein β subunit gene (Gβ) and found that the mutants are lethal, differing from those in Arabidopsis, in which homologous mutants have normal growth and fertility. We show that lethality is caused not by a specific developmental arrest, but by autoimmunity. We used a genetic diversity screen to suppress the lethal Gβ phenotype and also identified a maize Gβ allele with weak autoimmune responses but strong development phenotypes. Using these tools, we show that Gβ controls meristem size in maize, acting epistatically with G protein α subunit gene (Gα), suggesting that Gβ and Gα function in a common signaling complex. Furthermore, we used an association study to show that natural variation in Gβ influences maize kernel row number, an important agronomic trait. Our results demonstrate the dual role of Gβ in immunity and development in a cereal crop and suggest that it functions in cross-talk between these competing signaling networks. Therefore, modification of Gβ has the potential to optimize the trade-off between growth and defense signaling to improve agronomic production

Development of DNA markers for Slmlo1.1, a new mutant allele of the powdery mildew resistance gene SlMlo1 in tomato (Solanum lycopersicum)

Reductions in growth and quality due to powdery mildew (PM) disease cause significant economic losses in tomato production. Oidium neolycopersici was identified as the fungal species responsible for tomato PM disease in South Korea in the present study, based on morphological and internal transcribed spacer DNA sequence analyses of PM samples collected from two remote regions (Muju and Miryang). The genes involved in resistance to this pathogen in the tomato accession ‘KNU-12’ (Solanum lycopersicum var. cerasiforme) were evaluated, and the inheritance of PM resistance in ‘KNU-12’ was found to be conferred via simple Mendelian inheritance of a mutant allele of the PM susceptibility locus Ol-2 (SlMlo1). Full-length cDNA analysis of this newly identified mutant allele (Slmlo1.1) showed that a 1-bp deletion in its coding region led to a frameshift mutation possibly resulting in SlMlo1 loss-of-function. An alternatively-spliced transcript of Slmlo1.1 was observed in the cDNA sequences of ‘KNU-12’, but its direct influence on PM resistance is unclear. A derived cleaved amplified polymorphic sequence (dCAPS) and a high-resolution melting (HRM) marker were developed based on the 1-bp deletion in Slmlo1.1, and could be used for efficient marker-assisted selection (MAS) using ‘KNU-12’ as the source for durable and broad-spectrum resistance to PM.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Transposon Ac/Ds -induced chromosomal rearrangements at the rice OsRLG5 locus

Previous studies have shown that pairs of closely-linked Ac/Ds transposable elements can induce various chromosomal rearrangements in plant genomes. To study chromosomal rearrangements in rice, we isolated a line ( OsRLG5-161) that contains two inversely-oriented Ds insertions in OsRLG5 ( Oryza sativa Receptor like kinase Gene 5). Among approximately 300 plants regenerated from OsRLG5-161 heterozygous seeds, 107 contained rearrangements including deletions, duplications and inversions of various sizes. Most rearrangements were induced by previously identified alternative transposition mechanism. Furthermore, we also detected a new class of rearrangements that contain juxtaposed inversions and deletions on the same chromosome. We propose that these novel alleles were generated by a previously unreported type of alternative transposition reactions involving the 5′ and 3′ termini of two inversely-oriented Ds elements located on the same chromatid. Finally, 11% of rearrangements contained inversions resulting from homologous recombination between the two inverted Ds elements in OsRLG5-161 . The high frequency inheritance and great variety of rearrangements obtained suggests that the rice regeneration system results in a burst of transposition activity and a relaxation of the controls which normally limit the transposition competence of individual Ds termini. Together, these results demonstrate a greatly enlarged potential of the Ac/Ds system for plant chromosome engineering.This article is from Nucleic Acids Research 39 (2011): e149, doi: 10.1093/nar/gkr718. Posted with permission.</p