Os03g03150

Function

Tillering and Dwarf 1 (TAD1) encodes a co-activator of the anaphase-promoting complex (APC/C), a multi-subunit E3 ligase. It shows increased tillers and reduced plant height. TAD1 encodes a Cdh1-type activator of APC/C, an ortholog to CCS52A in dicots. During the cell-cycle progression, TAD1 shows an oscillating expression pattern with a higher level in the G1-phase. TAD1 interacts with MOC1, forming a complex with OsAPC10 and functions as a co-activator of APC/C to target MOC1 for degradation in a cell-cycle-dependent manner.

Mutation

The tad1 mutant showed an increased tiller number, a reduced plant height, and twisted leaves and panicles(Fig. 1a–e).

Sequence analysis revealed a single base substitute (TGG→TGA) at the second exon of LOC_Os03g03150 in tad1, which produces a premature stop codon. LOC_Os03g03150 is the TAD1 gene and the premature mutation is responsible for the phenotypes of the tad1 mutant plant. TAD1 is involved in regulating the exit of mitosis and it is indeed a functional cell-cycle switch protein homolo¬gous to Cdh1.

Expression

TAD1 is expressed ubiquitously in the examined rice organs, includ¬ing roots, shoot apices, axillary buds, internodes, nodes, and young leaves and panicles, but more abundant in young leaves, axillary buds and nodes. TAD1 was predominantly expressed in the leaf primordia and young leaves, tiller buds, inflorescence pro¬mordia, and crown root promordia. In addition, TAD1 expression was detected in vascular bundles at the unenlon¬gated stem. TAD1 has an oscillated expression pattern during the cell-cycle pro¬gression, showing a higher level in the G1-phase and a lower level in the S- and G2/M-phases. TAD1 most likely controls rice tillering through regulating MOC1. The 67-amino-acid N-terminal of TAD1 appears to be essential for its interaction with MOC1. TAD1 degrades MOC1 at the G1-phase. TAD1 recruits MOC1 to APC/C, and OsAPC10 is also involved in recognizing and target¬ing MOC1 for further degradation.

Evolution

The gene provides the identification and in-depth functional characterization of a specific component of the cell-cycle machinery in higher plants that regulates agronomically important traits, tillering and plant height to facili¬tate the genetic manipulation of plant architecture and the breeding of new varieties in agriculture in the future. Labs working on this gene: 1、State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China. 2、State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China. References：