Male sterility plays an important role in F1 hybrid seed production. We identified a male-sterile rice (Oryza sativa) mutant with impaired pollen development and a single T-DNA insertion in the transcription factor gene bHLH142. Knockout mutants of bHLH142 exhibited retarded meiosis and defects in tapetal programmed cell death. RT-PCR and in situ hybridization analyses showed that bHLH142 is specifically expressed in the anther, in the tapetum, and in meiocytes during early meiosis. Three basic helix-loop-helix transcription factors, UDT1 (bHLH164), TDR1 (bHLH5), and EAT1/DTD1 (bHLH141) are known to function in rice pollen development. bHLH142 acts downstream of UDT1 and GAMYB but upstream of TDR1 and EAT1 in pollen development. In vivo and in vitro assays demonstrated that bHLH142 and TDR1 proteins interact. Transient promoter assays demonstrated that regulation of the EAT1 promoter requires bHLH142 and TDR1. Consistent with these results, 3D protein structure modeling predicted that bHLH142 and TDR1 form a heterodimer to bind to the EAT1 promoter. EAT1 positively regulates the expression of AP37 and AP25, which induce tapetal programmed cell death. Thus, in this study, we identified bHLH142 as having a pivotal role in tapetal programmed cell death and pollen development.

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Oxidative stress and reduced pH are involved in many inflammatory diseases. This study describes a nanoparticle-based system that is responsive to both oxidative stress and reduced pH in an inflammatory environment to effectively release its encapsulated curcumin, an immune-modulatory agent with potent anti-inflammatory and antioxidant capabilities. Because of the presence of Förster resonance energy transfer between curcumin and the carrier, this system also allowed us to monitor the intracellular release behavior. The curcumin released upon triggering could efficiently reduce the excess oxidants produced by the lipopolysaccharide (LPS)-stimulated macrophages. The feasibility of using the curcumin-loaded nanoparticles for anti-inflammatory applications was further validated in a mouse model with ankle inflammation induced by LPS. The results of these studies demonstrate that the proposed nanoparticle system is promising for treating oxidative stress-related diseases.

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