Overexpression of Arabidopsis thaliana tryptophan synthase beta 1 (AtTSB1) in Arabidopsis and tomato confers tolerance to cadmium stress.
Tryptophan (Trp) is an essential amino acid in humans, and in plants, it plays a major role in the regulation of plant development and defence responses. However, little is known about Trp-mediated cadmium (Cd) tolerance. Gene expression analysis showed that Arabidopsis thaliana tryptophan synthase beta 1 (AtTSB1) is up-regulated in plants treated with Cd; hence, we investigated whether this gene is involved in Cd tolerance. Exogenous application of Trp to wild-type Arabidopsis enhances Cd tolerance. Cd tolerance in the Trp-overproducing mutant trp5-1 was associated with high chlorophyll levels and low lipid peroxidation, as indicated by malondialdehyde 4-hydroxyalkenal level, whereas the wild-type developed symptoms of severe chlorosis. Moreover, the Trp-auxotroph mutant trp2-1 was sensitive to Cd. CaMV 35S promoter-driven AtTSB1 enhanced Trp accumulation and improved Cd tolerance in transgenic Arabidopsis and tomato plants without increasing the level of Cd. Moreover, reverse transcription-polymerase chain reaction confirmed that enhanced level of Trp in AtTSB1 transgenic Arabidopsis plants affected the expression of AtZIP4 and AtZIP9 metal transporters, which interfered with Cd ion trafficking, a mechanism of transcriptional regulation that does not exist in wild-type plants. Overexpression of AtTSB1 in transgenic tomato also produced higher Trp synthase-beta enzyme activity than that in wild-type plants. These results implicate that Trp could be involved in Cd defence.
Sanjaya
Agricultural Biotechnology Research Center, Academia Sinica, Taiwan.
Hsiao
Pao-Yuan
PY
Su
Ruey-Chih
RC
Ko
Swee-Suak
SS
Tong
Chii-Gong
CG
Yang
Ray-Yu
RY
Chan
Ming-Tsair
MT
D000222:Adaptation, Physiological / Q000187:drug effects*; D017360:Arabidopsis / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002104:Cadmium / Q000633:toxicity*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018551:Solanum lycopersicum / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism; D014367:Tryptophan Synthase / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D002104:Cadmium; D014364:Tryptophan; D014367:Tryptophan Synthase