In plants, sugar demand/starvation, hormone and environmental signaling crosstalk modulates the majority of fundamental growth processes, but the detailed regulatory mechanisms are mostly unknown. Using rice as a research model, our studies focus on:
In plants, sugars produced in source tissues (photosynthetic leaves or storage organs) fuel cellular carbon and energy metabolisms in sink (growing tissues), while sugar demand/starvation signal in sink tissues stimulates photosynthesis and sucrose export in source tissues. Recently, we identified a negative regulator SKIN which modulates the dual function of the carbon/energy sensor SnRK1 in sugar and nutrient starvation signaling in rice developing and germinated seeds, particularly under drought stress. The mechanism of SKIN action in response to drought stress is studied.
Germination is a unique developmental transition from metabolically quiescent seed to actively growing seedling. We found two crucial transcription factors, MYBS1 and MYBGA, integrate diverse nutrient starvation and hormone gibberellin (GA) signaling to induce an ensemble of hydrolases for coordinated nutrient mobilization for supporting heterotrophic growth until autotrophic photosynthesis is established after cereal germination. How phosphorylation and nucleocytoplasmic shuttling of two MYBs in these processes are regulated and how two MYBs interact are studied.
Rice is unusually tolerant to flooding which causes O2 deficiency. We found that protein kinase CIPK15 regulates SnRK1 and links O2 deficiency signal to the sugar starvation signaling cascade to induce sugar and energy production, and thus enable rice growth under flood-water. How sugar and O2 deficiency signals are initiated and sensed by the Ca+2 sensor CBL which then interacts with CIPK15 to transmit the sugar starvation or O2 deficiency signal into physiological responses to allow rice to grow are under investigation.
By a T-DNA insertional mutagenesis approach, a rice mutant population containing 100,000 gene activation or knockout mutant lines and a database containing 60,000 T-DNA tagged sequences in the rice genome have been generated and used worldwide. These resources are valuable for rice gene function studies using forward and reverse genetics approaches. Genes control plant growth, stress responses and yield, and promoters responsive to stresses and regulating tissues-specific gene expression have been identified and characterized.
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