Gene expression analysis in cadmium-stressed roots of a low cadmium-accumulating solanaceous plant, Solanum torvum

Abstract

Solanum torvum Sw. cv. Torubamubiga (TB) is a low cadmium (Cd)-accumulating plant. To elucidate the molecular mechanisms of the Cd acclimation process in TB roots, transcriptional regulation was analysed in response to mild Cd treatment: 0.1 μM CdCl2 in hydroponic solution. A unigene set consisting of 6296 unigene sequences was constructed from 18 816 TB cDNAs. The distribution of functional categories was similar to tomato, while 330 unigenes were suggested to be TB specific. For expression profiling, the SuperSAGE method was adapted for use with Illumina sequencing technology. Expression tag libraries were constructed from Cd-treated (for 3 h, 1 d, and 3 d) and untreated roots, and 34 269 species of independent tags were collected. Moreover, 6237 tags were ascribed to the TB or eggplant (aubergine) unigene sequences. Time-course changes were examined, and 2049 up- and 2022 down-regulated tags were identified. Although no tags annotated to metal transporter genes were significantly regulated, a tag annotated to AtFRD3, a xylem-loading citrate transporter, was down-regulated. In addition to induction of heavy metal chaperone proteins, antioxidative and sulphur-assimilating enzymes were induced, confirming that oxidative stress developed even using a mild Cd concentration. Rapid repression of dehydration-related transcription factors and aquaporin isoforms suggests that dehydration stress is a potential constituent of Cd-induced biochemical impediments. These transcriptional changes were also confirmed by real-time reverse transcription-PCR. Further additions of TB unigene sequences and functional analysis of the regulated tags will reveal the molecular basis of the Cd acclimation process, including the low Cd-accumulating characteristics of TB.

A Transcriptomic Network Underlies Microstructural and Physiological Responses to Cadmium in Populus × canescens

“…In P. 3 canescens bark, decreased expression of these genes may contribute to reductions in nitrogen and phosphorus concentrations under cadmium exposure. In cadmium-treated herbaceous plants, decreased transcripts levels of genes involved in photosynthesis and carbohydrate metabolism has been observed (Mysliwa-Kurdziel et al, 2004;Herbette et al, 2006;Weber et al, 2006;Ogawa et al, 2009;Yamaguchi et al, 2010;Sandalio et al, 2012;Xu et al, 2012). In cadmium-exposed Populus tremula leaves, repression of essential proteins involved in the photosystem, chlorophyll biosynthesis, and carbohydrate metabolism has been detected (Kieffer et al, 2008(Kieffer et al, , 2009b.…”

“…Although transcriptional profiles have been studied in cadmium-treated herbaceous plants, including Arabidopsis, A. halleri, Solanum torvum, Solanum nigrum, and rice (Oryza sativa; Herbette et al, 2006;Weber et al, 2006;Ogawa et al, 2009;Yamaguchi et al, 2010;Romero-Puertas et al, 2012;Xu et al, 2012) and in zinc-exposed Populus 3 euramericana (Di Baccio et al, 2011), no information is available about transcriptomic regulation underlying the microstructural responses to cadmium in woody plants. Cadmium accumulation in vacuoles of P. 3 canescens bark cells indicates that some transporters for heavy metals may be involved in this process.…”

Stress hardening under long-term cadmium treatment is correlated with the activation of antioxidative defence and iron acquisition of chloroplasts in Populus

“…In fact, the translocation of Fe from roots to the shoots was negligible during the entire experimental period. This may be related to the Cd induced down-regulation of the expression the citrate transporter FRD3 in the root xylem parenchyma, which plays a key role in citrate efflux into the xylem and thus in the root-to-shoot Fe translocation [38]. As Fe translocation did not recover under the continued Cd stress, the driving force of the later recovery cannot originate from an increased Fe content in the shoot.…”

Effect of Cadmium onArabidopsis ThalianaMutants Tolerant to Oxidative Stress

“…CAT activity was reduced by Cd 2+ in pea (12,46) and pine roots (54), pea leaves (51), sunflower (32) and Arabidopsis leaves (6) and seedlings (50) and in alga Ulva lactuca (30). The opposite effect was observed in radish roots (63), Spartina densiflora (37), Arachis hypogaea seedlings (11) and in tobacco plants which overexpress a soybean OAcetylserine (thyol) lyase (OASTL, EC 2.5.1.47) (41). OASTL catalyses the final step in cysteine biosynthesis and increases cysteine levels and cadmium tolerance in transformants (41).…”

“…The expression of antioxidative enzymes in Solanum torvum Sw. cv. Torubamubiga -a low Cd-accumulating plant, was increased under mild cadmium treatment (63 (63). Glutathione is an essential thiol antioxidant.…”