Root targeted over-expression of the heavy metal tolerance genes TaPCS1 and AtHMA3 reduces arsenic (As) and cadmium (Cd) accumulation in aerial tissues of Oryza Sativa (Rice) Plants

Overview

Guo’s UCSD master’s thesis tests whether root-specific overexpression of heavy-metal tolerance genes can retain cadmium and arsenic in rice roots rather than aerial tissues. It is rice supply-chain mitigation evidence from a controlled hydroponic seedling experiment, not market occurrence evidence for rice grain. The arsenic treatment was As(III), but the tissue endpoint was ICP-MS after nitric-acid digestion, so the measured plant-tissue endpoint is treated here as total arsenic context rather than inorganic-arsenic occurrence.

Key numbers

The thesis compared Nipponbare wildtype rice plants against two TaPCS1-overexpressing lines (TaPCS1-1 and TaPCS1-2) and one AtHMA3-overexpressing line. Values were normalized to dry weight, using the source’s formula PPB * 0.003 Liters / dry weight in grams, and are described in the thesis as ug / gram-of dry-weight. The extracted text reports fold changes and p-values but does not provide a table of individual root/shoot concentration values, so no bar-chart values are estimated here.

The Figure 2 and Figure 3 captions in the extracted text appear to swap or mislabel the arsenic (As)/cadmium (Cd) figure titles relative to the Results paragraphs. This page records the source’s text-layer fold-change statements and flags the inconsistency rather than reconciling it by visual inspection.

Methods (brief)

Sterilized transgenic and wildtype rice seeds were germinated on Murashige and Skoog agar plates, then transferred to 2L hydroponic chambers with nutrient media for 3 weeks before metal treatment. TaPCS1 plants received 5 µM CdCl2 plus 10 µM As(III); AtHMA3 plants received 2 µM CdCl2. After 15 days, plants exposed to cadmium were washed with 5 mM CaCl2, and plants exposed to cadmium plus arsenic were also washed with 1 mM K2HPO4; roots and shoots were separated, dried at 37 °C for 7 days, digested in 3 mL of 70% nitric acid for 24 hours, heated in boiling water for 30 minutes, diluted to 3 mL, and analyzed by ICP-MS at the Donald Danforth Plant Science Center. Significance testing used one-tailed t-tests assuming unequal variance.

Related evidence

• Rice
• Cadmium
• Arsenic, Total
• Remediation evidence — drivers and interventions

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.