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Proc Natl Acad Sci U S A. 2016 Aug 9;113(32):8969-74. doi: 10.1073/pnas.1604849113. Epub 2016 Jul 27.

Loss of function at RAE2, a previously unidentified EPFL, is required for awnlessness in cultivated Asian rice.

Author information

  • 1Bioscience and Biotechnology Center, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8601, Japan;
  • 2Section of Plant Breeding and Genetics, School of Integrated Plant Sciences, Cornell University, Ithaca, NY 14853-1901;
  • 3Graduate School of Agriculture, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8601, Japan;
  • 4Faculty of Biotechnology, Fukui Prefectural University, 4-1-1 Eiheiji-Town, Fukui 910-1195, Japan;
  • 5Institute of Transformative Bio-Molecules, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602, Japan;
  • 6Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602, Japan;
  • 7National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan;
  • 8Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
  • 9Graduate School of Agriculture, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8601, Japan; morihito@agr.nagoya-u.ac.jp srm4@cornell.edu ashi@agr.nagoya-u.ac.jp.
  • 10Section of Plant Breeding and Genetics, School of Integrated Plant Sciences, Cornell University, Ithaca, NY 14853-1901; morihito@agr.nagoya-u.ac.jp srm4@cornell.edu ashi@agr.nagoya-u.ac.jp.
  • 11Bioscience and Biotechnology Center, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8601, Japan; morihito@agr.nagoya-u.ac.jp srm4@cornell.edu ashi@agr.nagoya-u.ac.jp.

Abstract

Domestication of crops based on artificial selection has contributed numerous beneficial traits for agriculture. Wild characteristics such as red pericarp and seed shattering were lost in both Asian (Oryza sativa) and African (Oryza glaberrima) cultivated rice species as a result of human selection on common genes. Awnedness, in contrast, is a trait that has been lost in both cultivated species due to selection on different sets of genes. In a previous report, we revealed that at least three loci regulate awn development in rice; however, the molecular mechanism underlying awnlessness remains unknown. Here we isolate and characterize a previously unidentified EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) family member named REGULATOR OF AWN ELONGATION 2 (RAE2) and identify one of its requisite processing enzymes, SUBTILISIN-LIKE PROTEASE 1 (SLP1). The RAE2 precursor is specifically cleaved by SLP1 in the rice spikelet, where the mature RAE2 peptide subsequently induces awn elongation. Analysis of RAE2 sequence diversity identified a highly variable GC-rich region harboring multiple independent mutations underlying protein-length variation that disrupt the function of the RAE2 protein and condition the awnless phenotype in Asian rice. Cultivated African rice, on the other hand, retained the functional RAE2 allele despite its awnless phenotype. Our findings illuminate the molecular function of RAE2 in awn development and shed light on the independent domestication histories of Asian and African cultivated rice.

KEYWORDS:

awn; convergent evolution; parallel domestication; rice; signal peptide

PMID:
27466405
PMCID:
PMC4987784
DOI:
10.1073/pnas.1604849113
[PubMed - in process]
Free PMC Article
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