Os10g0478000

The rice TAWAWA1 (TAW1) gene, a member of ALOG family, was identified as a  regulator of rice inflorescence architecture.

Annotated Information

Function

Fig 1. Characterization of taw1 dominant mutants .

Fig 2. Isolation of the TAW1 gene .

Fig 3. Expression pattern of TAW1 .

Fig 4. SVP subfamily MADS-box genes work downstream of TAW1 .

Fig 5. Phenotype of taw1-D2–introgressed Koshihikari BC5F2 plants .

In the dominant gain-of-function mutant tawawa1-D(Fig. 1), the activity of the inflorescence meristem (IM) is extended and spikelet specification is delayed, resulting in prolonged branch formation and increased numbers of spikelets. In contrast, reductions in TAWAWA1 (TAW1) activity cause precocious IM abortion and spikelet formation, resulting in the generation of small inflorescences. TAW1 encodes a nuclear protein of unknown function and shows high levels of expression in the shoot apical meristem, the IM, and the branch meristem (BMs). TAW1 expression disappears from incipient spikelet meristems (SMs). It is demonstrated that members of the SHORT VEGETATIVE PHASE subfamily of MADS-box genes function downstream of TAW1. Thus, TAW1 is proposed as a unique regulator of meristem activity in rice and regulates inflorescence development through the promotion of IM activity and suppression of the phase change to SM identity .

Expression

TAW1 contains a conserved domain and a nuclear localization signal. Indeed, TAW1 localizes to the nucleus and shows slight but significant activity as a transcriptional activator (Fig. 3 A and B). The spatiotemporal pattern of TAW1 mRNA accumulation was examined by in situ hybridization. During the vegetative phase of development, TAW1 was predominantly expressed in meristems, including the SAM, axillary meristems, and young leaves (Fig. 3 A and C). After transition to the reproductive phase, TAW1 mRNA continued to accumulate in the IM (Fig. 3D). The strongest signal was observed in BMs in the growing inflorescence (Fig. 3E). After initiation of the primary BMs, TAW1 expression gradually disappeared from the IM as it degenerated (Fig. 3F). In wild-type inflorescences, the signal intensity in the meristem gradually decreased and became undetectable at SM initiation (Fig. 3G). On the other hand, in taw1-D inflorescences, stronger TAW1 signals were detected, even at the stage when the SMs were formed in the wild-type plants (Fig. 3 H and I). Quantitative PCR analysis indicated that the levels of TAW1 expression in the mutant inflorescences roughly coincided with the severity of their phenotypes (Fig. 3J). These results imply that TAW1 functions to suppress SM identity and that its activity must be below a certain threshold level to allow SM specification. Interestingly, TAW1 expression is reduced in the vegetative shoot apices, leaves, and roots of taw1-D mutants compared with wild-type plants. These results suggest that the sequence surrounding the nDart1 insertion sites is necessary for fine-tuning the spatial and quantitative expression pattern of TAW1. It may be that positive regulators of SM identity interact with this sequence, which is located downstream of the transcribed region. It is also possible that nDart1 carries a sequence that functions as a transcriptional enhancer; however, this is unlikely because not all nDart1 insertions activate transcription. Unraveling the molecular mechanisms that regulate TAW1 transcription will shed light on the regulatory networks controlling rice inflorescence architecture.

The rice genes G1 and TH1 are ALOG family members that are expressed in the lemma, palea, and floral organs and control their identity and development. On the other hand, the Arabidopsis ALOG family genes LSH3/OBO1 and LSH4 are expressed in shoot organ boundary cells. The functions of LSH3/OBO1 and LSH4 are unknown; however, they induce the overproliferation of shoot meristems and the formation of extra organs when ectopically expressed. A plausible scenario is that at least some of the ALOG family proteins share conserved functions, but it may be that their distinctive expression patterns have led to divergent functions. The establishment of the machinery for meristem-specific expression may be a primary reason for the evolution of TAW1 as a major regulator of meristem activity and phase transition.

Evolution

TAW1 function might have evolved to ensure the production of sufficient numbers of spikelets. Unraveling the molecular function of TAW1 will provide an opportunity for a greater understanding of meristem activity and identity, which is a fundamental issue in plant biology. Furthermore, such knowledge could be exploited to further increase crop yields. In addition, TAW1 is of great interest with respect to the evolution of inflorescence architecture. TAW1 function may be essential for the development of compound inflorescences, in which the branching pattern is crucial .

Labs working on this gene

• Graduate School of Agriculture and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo 113-8657, Japan

References

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Structured Information

Gene Name	Os10g0478000
Description	Protein of unknown function DUF640 domain containing protein
Version	NM_001189280.1 GI:297727690 GeneID:9266624
Length	1426 bp
Definition	Oryza sativa Japonica Group Os10g0478000, complete gene.
Source	Oryza sativa Japonica Group ORGANISM Oryza sativa Japonica Group Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta; Spermatophyta; Magnoliophyta; Liliopsida; Poales; Poaceae; BEP clade; Ehrhartoideae; Oryzeae; Oryza.
Chromosome	Chromosome 10
Location	Chromosome 10:18345508..18346933
Sequence Coding Region	18345710..18346324
Expression	GEO Profiles:Os10g0478000
Genome Context	<gbrowseImage1> name=NC_008403:18345508..18346933 source=RiceChromosome10 preset=GeneLocation </gbrowseImage1>
Gene Structure	<gbrowseImage2> name=NC_008403:18345508..18346933 source=RiceChromosome10 preset=GeneLocation </gbrowseImage2>
Coding Sequence	<cdnaseq>atggagttcgtggcgcacgcggcggcgccggacagcccgcactcggacagcggcggaggaggagggggaatggcgacgggggcgacgtcggcgtcggcggcgggggcgtcgccgagcaggtacgagtcgcagaagcggcgggactggaacacgttcgggcagtacctccgcaaccaccggccgccgctgtcgctggcgcggtgcagcggcgcgcacgtcctggagttcctccgctacctggaccagttcggcaagaccaaggtgcacgcgccggcgtgccccttcttcggccacccggcgccgccggcgccgtgcccgtgcccgcttcgccaggcgtggggcagcctcgacgccctcgtcggccgcctccgcgccgcctacgaggagaacggcggccgccccgagaacaaccccttcggcgcccgcgccgtccgcctctacctccgcgaggtccgcgagcaccaggcgcgcgcacgcggcgtcagctacgagaagaagaagcgcaagaagccaccccacccctcctccgccgccgccgcgcacgacgacgccgccaacggcgccctccaccaccaccaccacatgccgccgcctcctcccggcgccgccgcctga</cdnaseq>
Protein Sequence	<aaseq>MEFVAHAAAPDSPHSDSGGGGGGMATGATSASAAGASPSRYESQ KRRDWNTFGQYLRNHRPPLSLARCSGAHVLEFLRYLDQFGKTKVHAPACPFFGHPAPP APCPCPLRQAWGSLDALVGRLRAAYEENGGRPENNPFGARAVRLYLREVREHQARARG VSYEKKKRKKPPHPSSAAAAHDDAANGALHHHHHMPPPPPGAAA</aaseq>
Gene Sequence	<dnaseqindica>610..1224#tatcggctccttctcgcccagcttttgctcacgtcacatcaccttccacctccacccctccactcgctcgctcgcttgcttgctccaattaatacctcttctccttctcccccagcaactagcttccttctccgcttttgcagctcgccgccgccgccgccgccgccgccgcgacacggcgcgcatatggtcgtcgtcgtcgtcgtcgtcgtcgctggagaagacgaagaaagatagtagacctgagctgggggggcggtgaattcgccggagagctagctaaggtgagtttcgttttcggtttcggtttcgatcgatttgttggtgcagatgcatctgggagctagagaactatttatagtggctgcggtgcggtgcggcgtcgccacgccgcgcacgcgctcgcccacgtcgcgcgcgcgcgggcgcgcgtccactctctctctctcttggaccactgcgcgcgcgggcgcgcgtcggcgtcgccacggcttctcaagaacgcgcgcgcgcgcactgattcccagatagatagatctatatctgttcgtcttcctcagctatggtgtggtggtggtggtggtgtttgtggtgttgtgcagatcgacgatggagttcgtggcgcacgcggcggcgccggacagcccgcactcggacagcggcggaggaggagggggaatggcgacgggggcgacgtcggcgtcggcggcgggggcgtcgccgagcaggtacgagtcgcagaagcggcgggactggaacacgttcgggcagtacctccgcaaccaccggccgccgctgtcgctggcgcggtgcagcggcgcgcacgtcctggagttcctccgctacctggaccagttcggcaagaccaaggtgcacgcgccggcgtgccccttcttcggccacccggcgccgccggcgccgtgcccgtgcccgcttcgccaggcgtggggcagcctcgacgccctcgtcggccgcctccgcgccgcctacgaggagaacggcggccgccccgagaacaaccccttcggcgcccgcgccgtccgcctctacctccgcgaggtccgcgagcaccaggcgcgcgcacgcggcgtcagctacgagaagaagaagcgcaagaagccaccccacccctcctccgccgccgccgcgcacgacgacgccgccaacggcgccctccaccaccaccaccacatgccgccgcctcctcccggcgccgccgcctgagccgagccgagcttgctccaagatcgccggaaaacgagctgctagcctcctacgcatgcactagttactccactccactccactccactatgatccctagctaggctgctcttgctactagcaaaactacggattaatctccatgcttgctactgctgctgctgctgctactgcatctaattaattaggttgattatttcct</dnaseqindica>
External Link(s)	NCBI Gene:Os10g0478000, RefSeq:Os10g0478000