Differences in meristem size and expression of branching genes are associated with variation in panicle phenotype in wild and domesticated African rice.
BACKGROUND
The African riceOryza glaberrimawas domesticated from its wild relativeOryza barthiiabout 3000 years ago. During the domestication process, panicle complexity changed from a panicle with low complexity inO. barthii, to a highly branched panicle carrying more seeds inO. glaberrima. To understand the basis of this differential panicle development between the two species, we conducted morphological and molecular analyses of early panicle development.


RESULTS
Using X-ray tomography, we analyzed the morphological basis of early developmental stages of panicle development. We uncovered evidence for a wider rachis meristem inO. glaberrimathan inO. barthii. At the molecular level, spatial and temporal expression profiles of orthologs ofO. sativagenes related to meristem activity and meristem fate control were obtained using in situ hybridization and qRT-PCR. Despite highly conserved spatial expression patterns betweenO. glaberrimaandO. barthii, differences in the expression levels of these early acting genes were detected.


CONCLUSIONS
The higher complexity of theO. glaberrimapanicle compared to that of its wild relativeO. barthiiis associated with a wider rachis meristem and a modification of expression of branching-related genes. Our study indicates that the expression of genes in themiR156/miR529/SPLandTAW1pathways, along with that of their target genes, is altered from the unbranched stage of development. This suggests that differences in panicle complexity between the two African rice species result from early alterations to gene expression during reproductive development.
UMR DIADE, IRD, 911, Avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France.|LMI RICE, IRD, USTH, National Key Laboratory for Plant Cell Biotechnology, Agronomical Genetics Institute, Pham Van Dong Road, Hanoi, Vietnam.
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UMR DIADE, IRD, 911, Avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France.
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Adam
Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, Vienna, Austria.
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Staedler
Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, Vienna, Austria.
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Schönenberger
UMR DIADE, IRD, 911, Avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France.
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Harrop
UMR DIADE, IRD, 911, Avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France.
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Tregear
LMI RICE, IRD, USTH, National Key Laboratory for Plant Cell Biotechnology, Agronomical Genetics Institute, Pham Van Dong Road, Hanoi, Vietnam.
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Do
LMI RICE, IRD, USTH, National Key Laboratory for Plant Cell Biotechnology, Agronomical Genetics Institute, Pham Van Dong Road, Hanoi, Vietnam.|UMR DIADE, Université de Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France.|Department of Biotechnology-Pharmacology, University of Science and Technology of Hanoi (USTH), 18 Hoang Quoc Viet Road, Hanoi, Vietnam.
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Gantet
UMR DIADE, IRD, 911, Avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France.
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Ghesquière
UMR DIADE, IRD, 911, Avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France.|LMI RICE, IRD, USTH, National Key Laboratory for Plant Cell Biotechnology, Agronomical Genetics Institute, Pham Van Dong Road, Hanoi, Vietnam.
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Jouannic
African rice; Branching; Meristem fate; Panicle; Tomography