An isopentenyl transferase transgenic wheat isoline exhibits less seminal root growth impairment and a differential metabolite profile under Cd stress

Abstract

Cadmium is one of the most important contaminants and it induces severe plant growth restriction. In this study, we analyzed the metabolic changes associated with root growth restriction caused by cadmium in the early seminal root apex of wheat. Our study included two genotypes: the commercial variety ProINTA Federal (WT) and the PSARK::IPT (IPT) line which exhibit high‐grade yield performance under water deficit. Root tips of seedlings grown for 72 h without or with 10 μM CdCl2 (Cd‐WT and Cd‐IPT) were compared. Root length reduction was more severe in Cd‐WT than Cd‐IPT. Cd decreased superoxide dismutase activity in both lines and increased catalase activity only in the WT. In Cd‐IPT, ascorbate and guaiacol peroxidase activities raised compared to Cd‐WT. The hormonal homeostasis was altered by the metal, with significant decreases in abscisic acid, jasmonic acid, 12‐oxophytodienoic acid, gibberellins GA20, and GA7 levels. Increases in flavonoids and phenylamides were also found. Root growth impairment was not associated with a decrease in expansin (EXP) transcripts. On the contrary, TaEXPB8 expression increased in the WT treated by Cd. Our findings suggest that the line expressing the PSARK::IPT construction increased the homeostatic range to cope with Cd stress, which is visible by a lesser reduction of the root elongation compared to WT plants. The decline of root growth produced by Cd was associated with hormonal imbalance at the root apex level. We hypothesize that activation of phenolic secondary metabolism could enhance antioxidant defenses and contribute to cell wall reinforcement to deal with Cd toxicity.

Isopentenyltransferases as master regulators of crop performance: their function, manipulation, and genetic potential for stress adaptation and yield improvement

“…Isopentenyltransferases are of particular importance for plant metal stress responses as their overexpression can result in improved heavy metal stress tolerance (Gomez Mansur et al, 2021; Thomas et al, 2005). Accordingly, IPT ‐induced CTKs in transgenic tobacco enhanced copper stress tolerance, and this was explained by an increased expression of a metallothionein‐like gene (Thomas et al, 2005).…”

“…Accordingly, IPT ‐induced CTKs in transgenic tobacco enhanced copper stress tolerance, and this was explained by an increased expression of a metallothionein‐like gene (Thomas et al, 2005). Likewise, a transgenic wheat line, overexpressing IPT under the SARK::IPT promoter, showed a lower reduction in root growth under cadmium stress, and this was attributed to the activation of phenolic secondary metabolism, increased antioxidant defences, and cell wall reinforcement (Gomez Mansur et al, 2021). Another study, using Arabidopsis, reported an opposite relationship whereby, CTK depletion plants ( ipt1,3,5,7 loss of function) gained selenium tolerance through the induced antioxidant enzyme activities and increased glutathione (GSH) content (Jiang et al, 2019).…”

Cloning and functional analysis of expansin TaEXPA9 orthologs in winter wheat in frigid regions

“…The TaEXPB8 gene can increase antioxidant defence by stimulating the secondary metabolism of phenols, having positive effects on cell wall strengthening at the same time. This enables the plant to respond to cadmium toxicity (Gomez Mansur et al 2021). In addition, expansins play crucial roles in plants under low-temperature stress.…”