Bioinformatic and functional analysis of OsDHN2 under cadmium stress.

As a toxic heavy metal, cadmium (Cd) is one of the principal pollutants influencing rice productivity and food security. Despite several studies, the underlying mechanism of Cd response in plants remains largely unclear. Dehydrins are part of the late embryogenesis abundant (LEA) family which protect plants against abiotic stresses. In this study, a Cd-responsive LEA gene, OsDHN2, was functionally characterized. The chromosome localization results indicated that OsDHN2 was located on chromosome 2 of rice. Meanwhile, cis-acting elements, such as MBS (MYB binding site involved in drought-inducibility), ARE (anaerobic induction), and ABRE (abscisic acid), were present in the OsDHN2 promoter region. Expression pattern analysis also showed that OsDHN2 expression was induced in both roots and shoots under Cd stress. Overexpression of OsDHN2 improved Cd tolerance and reduced Cd concentration in yeast. Moreover, increased expression levels of SOD1, CTA1, GSH1, or CTT1 were found in transgenic yeast under Cd stress, suggesting the increased antioxidant enzymatic activities. These results suggested that OsDHN2 is a Cd-responsive gene that has the potential to improve resistance to Cd in rice.

Rice NIN-LIKE PROTEIN 3 modulates nitrogen use efficiency and grain yield under nitrate-sufficient conditions.

Nitrogen (N) is an essential macronutrient for crop growth and yield. Improving the N use efficiency (NUE) of crops is important to agriculture. However, the molecular mechanisms underlying NUE regulation remain largely elusive. Here we report that the OsNLP3 (NIN-like protein 3) regulates NUE and grain yield in rice under N sufficient conditions. OsNLP3 transcript level is significantly induced by N starvation and its protein nucleocytosolic shuttling is specifically regulated by nitrate. Loss-of-function of OsNLP3 reduces plant growth, grain yield, and NUE under sufficient nitrate conditions, whereas under low nitrate or different ammonium conditions, osnlp3 mutants show no clear difference from the wild type. Importantly, under sufficient N conditions in the field, OsNLP3 overexpression lines display improved grain yield and NUE compared with the wild type. OsNLP3 orchestrates the expression of multiple N uptake and assimilation genes by directly binding to the nitrate-responsive cis-elements in their promoters. Overall, our study demonstrates that OsNLP3, together with OsNLP1 and OsNLP4, plays overlapping and differential roles in N acquisition and NUE, and modulates NUE and the grain yield increase promoted by N fertilizer. Therefore, OsNLP3 is a promising candidate gene for the genetic improvement of grain yield and NUE in rice.

[Characteristics of CO2 emission from Carex-dominated wetland in Poyang Lake in non-flooded period].

By using static chamber/gas chromatography, the CO2 fluxes in a Carex cinerascen-dominated wetland in the Poyang Lake Nanji Wetland National Nature Reserve were measured in nonflooded period (from September 2009 to April 2010). Two treatments were installed, i. e. , soil-plant system (TC) and aboveground plant removal (TJ), representing ecosystem respiration and soil respiration, respectively. There was an obvious seasonal variation in the ecosystem respiration and soil respiration. The respiration rate in treatment TC ranged from 89.57 to 1243.99 mg CO2 x m(-2) x h(-1), and that in TJ was from 75.30 to 960.94 mg CO2 x m(-2) x h(-1). Soil respiration accounted for 39% -84% of ecosystem respiration, with an average of 64%. Soil temperature was the main factor controlling the ecosystem respiration and soil respiration, explaining more than 80% of the respiration variance. The temperature coefficient (Q10), an index of temperature sensitivity for respiration, was 3.31 for ecosystem respiration and 2.75 for soil respiration. The Q10 value was higher in winter than in autumn and spring. No significant correlation was observed between soil moisture and CO2 fluxes. In non-flooded period, the C. cinerascens-dominated wetland acted as a carbon sink of atmospheric CO2, with a carbon uptake of 1717.72 g C x m(-2).