The trichomes of rice leaves are formed by the differentiation and development of epidermal cells.  Plant trichomes play an important role in stress resistance and protection against direct ultraviolet irradiation.  However, the development of rice trichomes remains poorly understood.  In this study, we conducted ethylmethane sulfonate (EMS)-mediated mutagenesis on the wild-type (WT) indica rice ‘Xida 1B’.  Phenotypic analysis led to the screening of a mutant that is defective in trichome development, designated lhl1 (less hairy leaf 1).  We performed map-based cloning and localized the mutated gene to the 70-kb interval between the molecular markers V-9 and V-10 on chromosome 2.  The locus LOC_Os02g25230 was identified as the candidate gene by sequencing.  We constructed RNA interference (LHL1-RNAi) and overexpression lines (LHL1-OE) to verity the candidate gene.  The leaves of the LHL1-RNAi lines showed the same trichome developmental defects as the lhl1 mutant, whereas the trichome morphology on the leaf surface of the LHL1-OE lines was similar to that of the WT, although the number of trichomes was significantly higher.  Quantitative real-time PCR (RT-qPCR) analysis revealed that the expression levels of auxin-related genes and positive regulators of trichome development in the lhl1 mutant were down-regulated compared with the WT.  Hormone response analysis revealed that LHL1 expression was affected by auxin.  The results indicate that the influence of LHL1 on trichome development in rice leaves may be associated with an auxin pathway.

Increasing attentions have been paid to mineral concentration decrease in milled rice grains caused by CO2 enrichment, but the mechanisms still remain unclear. Therefore, mineral (Ca, Mg, Fe, Zn and Mn) translocation in plant-soil system with a FACE (Free-air CO2 enrichment) experiment were investigated in Eastern China after 4-yr operation. Results mainly showed that: (1) elevated CO2 significantly increased the biomass of stem and panicle by 21.9 and 24.0%, respectively, but did not affect the leaf biomass. (2) Elevated CO2 significantly increased the contents of Ca, Mg, Fe, Zn, and Mn in panicle by 61.2, 28.9, 87.0, 36.7, and 66.0%, respectively, and in stem by 13.2, 21.3, 47.2, 91.8, and 25.2%, respectively, but did not affect them in leaf. (3) Elevated CO2 had positive effects on the weight ratio of mineral/biomass in stem and panicle. Our results suggest that elevated CO2 can favor the translocation of Ca, Mg, Fe, Zn, and Mn from soil to stem and panicle. The CO2-led mineral decline in milled rice grains may mainly attribute to the CO2-led unbalanced stimulations on the translocations of minerals and carbohydrates from vegetative parts (e.g., leaf, stem, branch and husk) to the grains.