Enhancing yield has been a major challenge of agriculture. In rice, tiller number is one of the important biomass and yield components. A maize mutant grassy tillers1 (gt1) increases lateral branches in maize. The GT1 gene encodes a class I homeodomain leucine zipper (HD-Zip) protein. In maize, the gt1 expression is induced by shading and is dependent on the activity of teosinte branched1 (tb1), a major domestication locus controlling tillering and lateral branching. To estimate the biological role and agricultural utility of gt1 in rice, rice homologue (OsGT1) has been isolated and its overexpressors and RNAi lines were generated. Field data showed that OsGT1 overexpressors reduced tillers and panicles while RNAi lines increased them, compared to wild type. Shade signal is an important factor in determining lateral branching. To understand the relationship between OsGT1 and shade avoidance, plants have been grown under 50% shading in the field. Also, double genetic combinations with phytochrome mutants (phyA, B, and C) are being examining for tillering phenotype. These ongoing researches will provide insights in determining the action of OsGT1 on branching and shade avoidance in rice.

Nitrogen in rice paddy soils and utilized as the major source for N-assimilation in rice crops. In roots, transcriptional activities of ammonium uptake and assimilation genes are highly sensitive to the availability of exogenous ammonium. However, little is known about the transcription factor genes that regulated by ammonium supply and its role to roots and plant developments. To study the transcription factor genes that involved in Ammonium response, two weeks old rice seedlings treated using Ammonium from 0 to 3 hours. Total RNA collected from each sample and samples were prepared for Agilent 8x60K microarray system. Based on the microarray data, we select transcription factor genes that highly affected by ammonium and selected knock out mutant candidates that used for phenotype screening.