Role of two-component elements in rice

    In contrast to Arabidopsis thaliana, which is a dicot (class Magnoliopsida), rice (Oryza sativa) is a monocot (class Liliopsida)(What's the difference?).Various lines of evidence suggest that the function of two-component elements may be distinct in these two plant classes (e.g. Giulini et al. 2004 Nature 430:1031-4). This preliminary project is to determine the role of these two-component genes in rice growth and development, with an emphasis on understanding their function in the panicle.

Figure 1: Morphology of rice (Source:www.plant-pictures.de)

The rice cytokinin signaling pathway (Figure 2) is most likley similar to that of Arabidopsis. We have focused on the disruption of the OsAHPs (Fig. 3), which are positive elements represented by only two genes in the rice genome, and the type-A OsRRs, which, at least in Arabidopsis are negative regulatyors of cytokinin signaling.

Figure 2: Proposed signaling pathway for cytokinin perception in rice.

Figure 3: A phylogentic analysis of Hpt genes from plants (from Hutchison et al, (2006) Plant Cell  18:3073-87). The pseudo-HPts (missing the target His residue) are depicted in blue and the rice authentic Hpts (contained the conserved His target site) are highlighted in red. 1000 bootstrap replicates were used to construct the N-J tree and bootstrap values as percent are marked on the consensus tree. The accession numbers for the sequenced used are as follows: Wheat sequences: TaHPt, AY342358; TaHP 2, BK005644; TaHP3, BK005645. Maize sequences: ZmHP1, AB024293; ZmHP2, AB024292; ZmHP3, AB089191. Pea sequence: PsHPt, AJ831475. Poplar sequences: Populus x canadensis hpt1, AJ841793; hpt2, AJ841794; hpt3, AJ841795; hpt4, AJ841796. Madagascar periwinkle, Catharanthus roseus sequence: CrHPt1, AF346308. Rice sequences: OsHpt2, Os08g44350; OsHpt3, Os09g39400; OsHpt1, Os01g54050; OsHpt4, Os05g09410; OsHpt5, Os05g44570. Yeast sequence YPD1, U62016. Note: Click on a rice gene to bring up its sequence.

We have first analyszed the expression of the genes involved in cytokinin biosynthesis, degradation and signaling using the NanoStrings technology, a highly accurate, relatively high throughput method for the analysis of gene expression. The results from this study are described in the reference noted below.

We are currently characterizing the effect of disruption of the OsAHPs and type-A OsRRs on rice growth and development.

Publications supported by this award:

Tsai YC, Weir NR, Hill K, Zhang W, Kim HJ, Shiu SH, Schaller GE, Kieber JJ. (2012) Characterization of genes involved in cytokinin signaling and metabolism from rice. Plant Physiol. 158:1666-84

Some manuscripts describing two-component elements in rice:

Du, L., Jiao, F., Chu, J., Jin, G., Chen, M., Wu, P. (2007) The two-component signal system in rice (Oryza sativa L.): a genome-wide study of cytokinin signal perception and transduction.
Genomics. 89:697-707

Schaller, G.E., Doi, K., Hwang, I., Kieber, J.J., Khurana, J.P., Kurata, N., Mizuno, T., Pareek, A., Shiu, S.H., Wu P., Yip, W.K. (2007) Nomenclature for two-component signaling elements of rice. Plant Physiol. 143:555-7.

Ito, Y. and Kurata, N. (2006) Identification and characterization of cytokinin-signalling gene families in rice. Gene 382: 57-65.

Pareek, A., Singh, A., Kumar, M., Kushwaha, H.R., Lynn, A.M., Singla-Pareek, S.L. (2006) Whole genome analysis of Oryza sativa l. reveals similar architecture of two-component-signaling-machinery with Arabidopsis. Plant Physiol.142(2):380-97.

Jain, M., Tyagi, A.K., Khurana, J.P. (2006) Molecular characterization and differential expression of cytokinin-responsive type-A response regulators in rice (Oryza sativa). BMC Plant Biol. 6:1

This project is supported by the National Research Initiative or Agriculture and Food Research Initiative Competitive Grants Program grant no. 2011–67013–30069 from the USDA National Institute of Food and Agriculture