The Evolutionary History of Ehrhartoideae, Oryzeae, and Oryza

Abstract

Rice is a member of the genus Oryza, which has a history extending back into the Miocene. Oryza is in turn a member of the tribe Oryzeae, which along with the tribe Ehrharteae is included in the subfamily Ehrhartoideae. This paper reviews current knowledge of the genus, tribe and subfamily, and places rice in the larger evolutionary context of the entire grass family. The morphological characteristics of rice are an amalgam of characters that have originated at different times in its long evolutionary history. Increasingly, genomic characteristics are also being placed in a broad evolutionary context and it is becoming possible see which are characteristic of all grasses and which are more restricted to the genus Oryza or even to rice itself.

The homeotic gene long sterile lemma ( G1 ) specifies sterile lemma identity in the rice spikelet

“…If so, it is surprising that the sterile lemma of both O. sativa and ancestral species of O. grandiglumis has maintained the potential to express genes responsible for lemma identity for a long evolutionary period. The genus Leersia, which, like Oryza, belongs to Oryzeae, lacks the sterile lemma (16). It would be interesting to know whether G1 activity is involved in developmental arrest of the sterile lemma in this genus.…”

“…It is possible that G1 orthologs may be involved in morphological modification of the sterile lemma in lineages other than those of Oryza evolution. Alternatively, G1 function may be restricted to the sterile lemma of Oryza, because the epidermal convex structures (i.e., tubercles), which are suppressed by G1 in the sterile lemma, are a synapomorphy of the Oryza genus (16,30) and/or G1-related proteins may have diverse functions as a result of the insertion of amino acids, which are highly variable among grasses.…”

“…Stamen identity and floral meristem determinacy, which are controlled by a single C class gene, AGAMOUS, in Arabidopsis, are regulated separately by two or more C class genes that were duplicated before divergence of the grass species (12,13). The palea and lemma are organs specific to grasses, and enclose inner floral organs (14)(15)(16). The LEAFY HULL STERILE1 (LHS1) gene is involved in partially specifying the identity of the lemma and palea in rice, in addition to regulating spikelet meristem determinacy (17,18).…”

The Complete Plastid Genome Sequence of the Wild Rice Zizania latifolia and Comparative Chloroplast Genomics of the Rice Tribe Oryzeae, Poaceae

“…It comprises of many economically important cereals in the grass family, such as rice (Oryza sativa), corn (Zea mays), wheat (Triticum aestivum), and sorghum (Sorghum bicolor). An evolutionary framework has been thoroughly established at the family level based on multiple phylogenetic studies (Clark et al, 1995;GPWG, 2001;Duvall et al, 2007;BouchenakKhelladi et al, 2008;Vicentini et al, 2008;Kellogg, 2009). Poaceae has been classified into some basal lineages as well as two main lineages including the PACMAD clade (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae, and Danthonioideae) and the BEP clade (Bambusoideae, Ehrhartoideae, and Pooideae) (GPWG, 2001;Duvall et al, 2007;Bouchenak-Khelladi et al, 2008;Kellogg, 2009).…”

An investigation of lemma micromorphology in Thai Oryzeae (Poaceae)

“…Accordingly, various investigations into the morphology 2 , anatomy 3 , cytology 4 , and molecular phylogenetics [5][6][7] of the tribe have been published. The consensus of these and other studies is that tribe Oryzeae belongs in subfamily Ehrhartoideae, one of three subfamilies of the BEP (Bambusoideae, Ehrhartoideae, and Pooideae) clade 8,9 . In Thailand, four genera of Oryzeae are found 10 : Oryza L., Leersia Sw., Hygroryza Nees, and Zizania L. The genus Oryza contains five species and two varieties, while Hygroryza is a monotypic genus containing only H. aristata Nees.…”