OsTCP19 influences developmental and abiotic stress signaling by modulating ABI4-mediated pathways

Class-I TCP transcription factors are plant-specific developmental regulators. In this study, the role of one such rice gene, OsTCP19, in water-deficit and salt stress response was explored. Besides a general upregulation by abiotic stresses, this transcript was more abundant in tolerant than sensitive rice genotypes during early hours of stress. Stress, tissue and genotype-dependent retention of a small in-frame intron in this transcript was also observed. Overexpression of OsTCP19 in Arabidopsis caused upregulation of IAA3, ABI3 and ABI4 and downregulation of LOX2, and led to developmental abnormalities like fewer lateral root formation. Moreover, decrease in water loss and reactive oxygen species, and hyperaccumulation of lipid droplets in the transgenics contributed to better stress tolerance both during seedling establishment and in mature plants. OsTCP19 was also shown to directly regulate a rice triacylglycerol biosynthesis gene in transient assays. Genes similar to those up- or downregulated in the transgenics were accordingly found to coexpress positively and negatively with OsTCP19 in Rice Oligonucleotide Array Database. Interactions of OsTCP19 with OsABI4 and OsULT1 further suggest its function in modulation of abscisic acid pathways and chromatin structure. Thus, OsTCP19 appears to be an important node in cell signaling which crosslinks stress and developmental pathways.