Dynamic cytokinin signaling and function of auxin in cytokinin responsive domains during rice crown root development.

KEY MESSAGE: We reveal the onset and dynamic tissue-specific cytokinin signaling domains and functional importance of auxin in the auxin-cytokinin interaction domains in shaping root architecture in the economically important rice plant. Plant hormones such as auxin and cytokinin are central regulators of root organogenesis. Typical in the grass species, the root system in rice is primarily composed of post-embryonic adventitious/crown roots (ARs/CRs). Antagonistic auxin-cytokinin activities mutually balance each other to ensure proper root development. Cytokinin has been shown to inhibit crown root initiation in rice; albeit, the responsive domains remain elusive during the initiation and outgrowth of crown root primordia (CRP). Here, we show the cytokinin response domains during various stages of CRP development. RNA-RNA in situ hybridization and protein immunohistochemistry studies of the reporter gene expressed under the cytokinin responsive synthetic promoter revealed detailed spatio-temporal cytokinin signaling domains in the developing CRP. Furthermore, rice lines genetically depleted for endogenous auxin in the cytokinin responsive domains provided insight into the functional importance of auxin signaling during crown root development. Thus, our study demonstrates the onset and dynamic tissue-specific cytokinin response and functional significance of auxin-cytokinin interaction during root architecture formation in rice, a model grass species.

Genome-Wide Transcript Profiling Reveals an Auxin-Responsive Transcription Factor, OsAP2/ERF-40, Promoting Rice Adventitious Root Development.

Unlike dicots, the robust root system in grass species largely originates from stem base during postembryonic development. The mechanisms by which plant hormone signaling pathways control the architecture of adventitious root remain largely unknown. Here, we studied the modulations in global genes activity in developing rice adventitious root by genome-wide RNA sequencing in response to external auxin and cytokinin signaling cues. We further analyzed spatiotemporal regulations of key developmental regulators emerged from our global transcriptome analysis. Interestingly, some of the key cell fate determinants such as homeodomain transcription factor (TF), OsHOX12, no apical meristem protein, OsNAC39, APETALA2/ethylene response factor, OsAP2/ERF-40 and WUSCHEL-related homeobox, OsWOX6.1 and OsWOX6.2, specifically expressed in adventitious root primordia. Functional analysis of one of these regulators, an auxin-induced TF containing AP2/ERF domain, OsAP2/ERF-40, demonstrates its sufficiency to confer the adventitious root fate. The ability to trigger the root developmental program is largely attributed to OsAP2/ERF-40-mediated dose-dependent transcriptional activation of genes that can facilitate generating effective auxin response, and OsERF3-OsWOX11-OsRR2 pathway. Our studies reveal gene regulatory network operating in response to hormone signaling pathways and identify a novel TF regulating adventitious root developmental program, a key agronomically important quantitative trait, upstream of OsERF3-OsWOX11-OsRR2 pathway.

Photocatalytic Degradation of Bisphenol-A using N, Co Codoped TiO2 Catalyst under Solar Light.

Advanced oxidation processes (AOPs) including heterogeneous photocatalysis has proven as one of the best technique for waste-water treatment. Photocatalytic process using semiconductor like TiO2 based heterogeneous photocatalysis is a promising method for the treatment of toxic pollutants. In the present study, visible-light photoactive cobalt and nitrogen co-doped TiO2 nanoparticles were synthesized via wet impregnation method. The photocatalysts were characterized using X-ray diffraction (XRD), Raman Spectra, Fourier Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), UV-vis spectrophotometer and X-ray photoelectron spectrophotometer (XPS). The photocatalytic activitiy of prepared (N, Co)-codoped TiO2 on the mineralization of Bisphenol-A (BPA) under visible light irradiation was studied and the results were compared to commercial TiO2 (Degussa P25). The results demonstrated that 1.5% Co and 0.5% N - codoped TiO2 samples revealed higher activity than commercial TiO2. Total organic carbon (TOC) removal was observed to be 97%, which indicate the complete mineralization of BPA. GC-MS analysis was carried to find out the possible intermediates formed and reaction pathway.