Guangdeng Chen

Cadmium adsorption, chelation and compartmentalization limit root-to-shoot translocation of cadmium in rice ( Oryza sativa L.)

Strategies to reduce cadmium (Cd) in rice grain, below concentrations that represent serious human health concerns, require that the mechanisms of Cd distribution and accumulation within rice plants be established. Here, a comprehensive hydroponic experiment was performed to investigate the differences in the Cd uptake, chelation and compartmentalization between high (D83B) and low (D62B) Cd-accumulation cultivars contrasting in Cd accumulation in order to establish the roles of these processes in limiting Cd translocation from root to shoot. D83B showed 3-fold higher Cd accumulation in the shoots than the cultivar D62B. However, a short-term Cd uptake experiment showed more Cd uptake by D62B than by D83B. The distribution of Cd in roots and shoots differed significantly. D83B translocated 38% of total Cd taken up to the shoots, whereas D62B retained most of the Cd in the roots. D62B had higher amounts of non-protein thiols (NPTs) and glutathione (GSH) than D83B. The NPT and Cd distribution ratio (CDR) in the anionic form in the roots of D62B increased gradually as Cd concentration increased. In D83B, in contrast, levels of CDR in the cationic form increased significantly from 22.10 to 43.37%, while NPT only increased slightly. Furthermore, the percentage of Cd ions retained in thiol-rich peptides, especially in the HMW complexes, was significantly higher in D62B compared with D83B. However, D83B possessed a greater proportion of potentially mobile (cationic) Cd in the roots and showed superior Cd translocation from root to shoot. Taken as a whole, the results presented in this study revealed that Cd chelation, compartmentalization and adsorption contribute to the Cd retention in roots.

Quantitative trait locus analysis of adventitious and lateral root morphology of barley grown at low and high P

Barley (Hordeum vulgare L) may alter its root morphology to improve P acquisition efficiency under low-P (LP) stress. This research studied the variations in adventitious and lateral root morphological traits of barley and mapped their quantitative trait loci (QTLs) under LP and high P (HP). The recombinant inbred lines were derived from the F1 population of a cross between CN4027 and Baudin. Two experiments aimed to identify QTLs related to adventitious and lateral root morphological traits under LP and HP. The length, surface area and volume of adventitious and lateral roots were measured. Under HP, Baudin had larger root morphology, especially lateral root morphology, than CN4027. LP stress induced lateral root growth but inhibited adventitious root growth. Nineteen QTLs for root morphological traits were detected. These QTLs clustered within four regions (Cl-2H, Cl-3H, Cl-4H and Cl-7H) on chromosomes 2H, 3H, 4H and 7H, with corresponding contributions of 12.0-42.9%. Some QTLs are linked with the QTLs for P efficiency detected previously, demonstrating the role of root morphological traits in P efficiency. The Cl-2H region was identified in the interval bPb3927665-bPb3265744 on chromosome 2H and had major effects on lateral root growth, especially under LP. Lateral root length and surface area increased when alleles from Baudin were present at the QTLs in Cl-2H. This study demonstrated the patterns of growth among root types and the role of lateral roots in barleys adaption to LP stress. The QTL clusters, especially Cl-2H, may offer clues for fine mapping and map-based cloning.