TheYABBYGeneTONGARI-BOUSHI1Is Involved in Lateral Organ Development and Maintenance of Meristem Organization in the Rice Spikelet

Abstract

The meristem initiates lateral organs in a regular manner, and proper communication between the meristem and the lateral organs ensures the normal development of plants. Here, we show that mutation of the rice (Oryza sativa) gene TONGARI-BOUSHI1 (TOB1) results in pleiotropic phenotypes in spikelets, such as the formation of a cone-shaped organ instead of the lemma or palea, the development of two florets in a spikelet, or premature termination of the floret meristem, in addition to reduced growth of the lemma or palea and elongation of the awn. These phenotypes seem to result from not only failure in growth of the lateral organs, but also defects in maintenance and organization of the meristem. For example, the coneshaped organ develops as a ring-like primordium from an initial stage, suggesting that regulation of organ initiation in the meristem may be compromised. TOB1 encodes a YABBY protein, which is closely related to FILAMENTOUS FLOWER in Arabidopsis thaliana, and is expressed in the lateral organ primordia without any patterns of polarization. No TOB1 expression is detected in the meristem, so TOB1 may act non-cell autonomously to maintain proper meristem organization and is therefore likely to play an important role in rice spikelet development.

Jasmonic acid regulates spikelet development in rice

“…Furthermore, LONG STERILE LEMMA (G1), a member of a plant-specific gene family that contains proteins with an uncharacterized ALOG (Arabidopsis LSH1 and Oryza G1) domain, specifies rice spikelet morphology by determining sterile lemma identity 50 . TONGARI-BOUSHI 1 (TOB1), a YABBY protein, controls proper lateral organ development and spikelet meristem maintenance in a noncell-autonomous manner 51 . Whether the JA pathway interacts with these genes in regulating rice spikelet development remains to be elucidated.…”

RiceLHS1/OsMADS1Controls Floret Meristem Specification by Coordinated Regulation of Transcription Factors and Hormone Signaling Pathways

“…Our data suggest that OsMADS1 aids rice FM development and determinacy possibly by regulating genes like OsHB4/HD-Zip III and OsYABBY5/TONGARI-BOUSHI1 (TOB1). A recent study demonstrated a role for TOB1 (OsYABBY5) in rice FM maintenance and determinacy (Tanaka et al, 2012). As loss-of-function mutants in all rice HD-Zip III genes are not known, a complete understanding of their functions is awaited.…”

A homolog of Blade-On-Petiole 1 and 2 (BOP1/2) controls internode length and homeotic changes of the barley inflorescence

“…Both TF classes regulate KNOX gene expression in a shared pathway together with AtBOP1/2 and are repressed in Arabidopsis leaves and bracts (Norberg et al, 2005;Ha et al, 2007;Jun et al, 2010). Mutations of members belonging to these TF families are associated with changes in the spatiotemporal expression of KNOX genes causing pleiotropic alterations in the rice inflorescences: (1) elongated panicles (Horigome et al, 2009); (2) reduced growth of the lemma and palea; and (3) alterations in the number and identity of floral organs (Horigome et al, 2009;Xiao et al, 2009;Tanaka et al, 2012). These analogies in rice and barley anatomy and the similarities in the regulatory networks among rice and Arabidopsis may again imply that BOP gene regulatory pathways are partially conserved between monocot and dicot plants, suggesting that the barley BOP-like gene HvLax-a could fulfill a central function in controlling meristem identity, as BOP1/2 does in Arabidopsis.…”