![]() ![]() In addition, substantial deviation from neutral expectations was also observed at the promoter region of sh4 gene in African cultivated rice. barthii, suggesting that it was a target of selection during domestication. ![]() Further investigation based on the promoter region of the sh4 gene showed that nucleotide diversity of African cultivated rice is obviously lower at this locus than that of its wild progenitor O. barthii, while no transcription is detected in African cultivated rice. Although the causative mutation reported in Asian rice is not found in African rice ( Wang et al., 2014), RNA-seq from the panicle tissue revealed that the ortholog of sh4 is expressed in the wild progenitor O. ![]() The African rice ortholog of the major rice shattering gene sh4 may also be important in the reduced shattering of this species. These observations suggest the possibility that selection for a deletion of the OsSh1 ortholog might have contributed to the evolution of nonshattering phenotype in cultivated African rice. Interestingly, the genome of cultivated African rice harbors a ~ 45-kb deletion which leads to the absence of the ortholog of OsSh1 and three additional genes, whereas the ortholog of OsSh1 is present in the wild ancestor, O. In the case of OsSh1, a ~ 4-kb insertion found at the third intron in Asian rice leads to the decreased expression level of OsSh1 that results in a nonshattering phenotype compared to the wild progenitor O. (2014) have compared the gene structures and expression patterns of three shattering-related genes, OsSh1, sh4, and qSH1, between African and Asian cultivated rice based on whole genome data ( Table 1). However, as a congeneric species that is phylogenetically close to its Asian counterpart, orthologs of genes that control shattering in Asian rice have been proposed to show similar functions in African rice. The molecular mechanisms underlying the reduced-shattering phenotype of African rice remain less resolved than Asian rice. Most relevant to the present discussion, the seed of African rice shatters more easily than that of Asian rice. In comparison with Asian rice, for example, African rice usually has small grains that are pear-shaped and have a red bran (pericarp) and an olive-to-black seed coat, straight panicles, and short ligules ( Linares, 2002). Although African rice and Asian rice were domesticated independently from distinct wild progenitors, only slight morphological differences are observed between them ( Linares, 2002). At the present time, African rice is mainly cultivated in tropical West Africa and has been largely displaced on that continent by Asian rice cultivation ( Semon, Nielsen, Jones, & McCouch, 2005). The latter was supported by a recent population genomic study based on a total of 114 African rice accessions ( Wang et al., 2014). In contrast, Fage and Oliver (1970) and Porteres (1962) proposed an alternative hypothesis that African rice primarily originated from the Inland Delta of the Upper Niger River and was then dispersed to two secondary centers along the Sahelian Rivers. Harlan (1971) proposed that African rice was selected by ancient hunting–gathering human populations from distinct places within the vast forest and savanna areas. Archeological evidence, including ceramic impressions of rice grains, suggests that this domestication may have occurred 2000–3000 YA ( Klee, Zach, & Neumann, 2000). glaberrima) is thought to have been domesticated from the African wild rice species Oryza barthii ( Sarla & Swamy, 2005 Sweeney & McCouch, 2007 Wang et al., 2014). Olsen, in Current Topics in Developmental Biology, 2016 3.1.2 African Rice (O. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |