Os03g0232600

TUD1, encoding a functional U-box E3 ubiquitin ligase, acts together with D1 to mediate a BR signaling pathway in rice to affect plant growth and development.

Annotated Information

Function

1. TUD1 functions together with D1 in the plasma membrane(figure7) we discovered a D1 genetic interactor Taihu Dwarf1(TUD1) that encodes a U-box E3 ubiquitin ligase. Such ligases are important regulators of cell functions. Genetic and molecular analyses revealed that D1 and TUD1 genetically and physically interact with each other and function together to regulate BR-mediated growth in rice. Furthermore, similar genes toTUD1 are found in both Arabidopsis and other cereal species, such as Sorghum bicolor and Zea mays. G-protein signaling mediated by TUD1, therefore, may be conserved across flowering plants. Such key signaling molecules may provide a target to increase plant productivity by modulating the strengths of signals controlling growth in different tissues such as the seed grain.

2. Potential application of the D1-TUD1-mediated signaling pathway in enhancing rice yield D1 and TUD1 function together not only to promote plant height, panicle development and seed length increase, but also to control a hypersensitive response to infection by avirulent races of a rice blast fungus (our unpublished data). Based on the D1-TUD1-mediated pathway having dual roles in promoting plant growth and resistance to rice blast, it may be feasible to manipulate the components of this pathway to enhance rice yield.

Expression

TUD1 encodes a functional U-box E3 ligase. Transformants with the TUD1gene-containing vector showed phenotypes similar to wild-type plants, while transformants with the control vector containing no target gene did not (Figure 6B). Thus, tud1 was caused by a loss-of-function mutation in a U-box gene.

Mutation

A dwarf mutant similar to d1 was identified and subsequently shown to be non-allelic to d1 and we named this dwarf mutant taihu dwarf1 (tud1). The double mutant showed that tud1 and d61 had an additive effect on rice growth and development. These results showed that TUD1 acts in the same genetic pathway as D1. The phenotype of the double mutant(d1 and tud1) was similar to tud1-5 with a specific reduction of the second internode length, erect leaves and shortened grain lengths (Figure 1A–1C).

1.tud1 is a pleiotropic dwarf mutant We compared the gross morphology of 9-week-old wild-type and tud1 plants (Figure 2A). The plant heights of tud1 mutants were significantly shorter than their corresponding wild type, and tud1-5 showed a severe dwarf phenotype. Lengths of the individual internodes of plants were measured and expressed as a relative value (Figure 2B). Among them, tud1-1, tud1-2, and tud1-5 showed a specific intermodal inhibition; the second internode was severely shortened relative to other internodes. In addition, either unhulled or hulled seeds were specifically shortened in the vertical direction in tud1 mutants (Figure 2C). Compared with their corresponding wild type, the grain lengths oftud1mutants were reduced by 30 to 44%. Their leaves were also shortened, erect and dark-green, similar to d1, but their severe rugose (curled) nature appeared to be different from d1(Figure 2D).

To determine whether dwarfism intud1 was due to cell division, cell elongation or both, we measured the cell length and number in the third leaf sheath, the third internode and the lemma of tud1-2 and its wild type (Figure 3A–3C). Overall we found that the total number of cells, in all given organs, was reduced in the mutant compared to wild type.

Localization

1.TheTUD1locus was first mapped to the short arm of chromosome 3 between markers s1193411 and s32681 (Figure 6A). TUD1was further localized to an 18.457 kb region containing three open reading frames (Figure 6A).

2.To investigate the subcellular localization of TUD1, we conducted an in-vivo targeting experiment using fusions of TUD1 with synthetic green fluorescent protein (sGFP) as a fluorescent marker in a transient transfection assay. The TUD1::sGFP fusion protein in rice protoplasts was mainly associated with the plasma membrane (Figure 7A), similar to that of D1.

Labs working on this gene

1.State Key Laboratory of Molecular Developmental Biology, Chinese Academy of Sciences and National Center for Plant Gene Research, Beijing, China

2.National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China

3.Graduate University, Chinese Academy of Sciences, Beijing, China

4.State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences and National Center for Plant Gene Research, Beijing, China

References

1.Hu X, Qian Q, Xu T, Zhang Y, Dong G, et al. (2013) The U-Box E3 Ubiquitin Ligase TUD1 Functions with a Heterotrimeric GaSubunit to Regulate Brassinosteroid-Mediated Growth in Rice. PLoS Genet 9(3): e1003391. doi:10.1371/journal.pgen.1003391

2.Temple BRS, Jones AM (2007) The plant heterotrimeric G-protein complex. Annu Rev Plant Biol 58: 249–266.

3. Kato C, Mizutani T, Tamaki H, Kumagai H, Kamiya T, et al. (2004) Characterization of heterotrimeric G protein complexes in rice plasma membrane. Plant J 38: 320–331