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Cadmium (Cd) is toxic to the ecosystem even at low concentrations. To mitigate Cd toxicity as well as to enhance plant growth, endophytes extracted from different sources have been effectively used. In the current study, the role of an endophytic bacterial strain Serratia sp. IU01, in alleviating Cd toxicity and promoting growth was evaluated in Brassica juncea in the hydroponic system. Cd stress significantly reduced the growth attributes (root/shoot length and biomass) of the host plant in comparison to control plants. A significant increase was observed in the shoot, root length and biomass of B. juncea plants inoculated with Serratia sp. IU01 (9.8 ± 0.28 cm, 12.16 ± 1.44 cm, 299.5 ± 39.5 mg, respectively) compared to control (8.6 ± 0.28 cm, 7.16 ± 0.76 cm, 125.27 ± 5.40 mg, respectively), sole Cd-treated (5.5± 0.5 cm, 4.33± 1.15 cm, 103.73 ± 7.18 mg, respectively), and inoculated Cd-treated plants (5.67± 0.58 cm, 6± 1.53 cm, 137.33 ± 6.66 mg, respectively). Growth parameters were retrieved in inoculated plants under Cd stress but the differences were non-significant in comparison to the un-inoculated Cd-treated plants. High-performance liquid chromatography (HPLC) analysis revealed significantly elevated steady-state levels of one of the most abundant versatile antioxidant molecules in the cell i.e., glutathione (GSH) in response to Cd stress. However, under Cd stress, inoculation of the plants with Serratia sp. IU01 led to a significant decrease in roots' GSH contents (75 ± 15.56 pmol mg-1 FW) compared with the un-inoculated Cd-treated (141 ± 7.2 pmol mg-1 FW) and control set of plants (123.6 ± 1.2 pmol mg-1 FW) presumably via the release of antioxidants by the endophytes in the roots of internal tissues of the host plant. These results demonstrated the potential of Serratia sp. IU01 in mitigating Cd-induced toxicity and promoting plant growth in Cdpolluted environments. [ABSTRACT FROM AUTHOR]

Among the toxic heavy metal(loid)s, cadmium (Cd) and arsenic (As) have devastating effects on crop productivity and human health. In plants, mechanisms of detoxification of Cd and As proceed via a glutathione (GSH) dependent common pathway, despite their different modes of toxicity. In this context, the present study aimed to investigate how the common detoxification mechanisms for Cd and As influence the physiological and biochemical responses of seedlings of an important plant used for phytoremediation purposes, Brassica juncea, under Cd and As stress.We demonstrated that Cd and As trigger mostly distinct, but partly overlapping, responses in B. juncea. Exposure of B. juncea seedlings to 100 µM Cd stress for 12 days in a hydroponic system led to a significant reduction in the growth of roots and shoots, and in total chlorophyll content. However, As stress caused a decline in root length only. High-performance liquid chromatography analyses revealed a significant increase in cysteine levels in roots and shoots in response to As stress compared with control and Cd-treated plants. Concomitant elevated sulfur content in response to As stress was observed in roots and shoots. In terms of GSH content, Cd and As triggered similar responses, with a significant decrease in GSH in roots, and non-significant changes in shoots, compared with untreated plants. Inductively coupled plasma-atomic emission spectroscopy revealed that under Cd stress, plants preferentially accumulated zinc (Zn) in the roots compared with iron (Fe) and manganese (Mn). Responses in roots under As and Cd stress were similar with respect to Fe accumulation but opposite in terms of Zn and Mn accumulation. Our data provide valuable insights for design of future strategies for sustainable plant growth on As and Cd polluted soils. [ABSTRACT FROM AUTHOR]

Serine acetyltransferase (SAT) (EC 2.3.1.30) is the rate-limiting enzyme of cysteine (Cys) biosynthesis, providing the decisive precursor for the ubiquitous defense thiol glutathione (GSH). Together with O -acetylserine (thiol) lyase (OAS-TL; EC 2.5.1.47) SAT generates Cys in the cytosol, plastids, and mitochondria of vascular plants. The current study aimed to overproduce Cys and GSH for enhanced stress tolerance via overexpression of the feedback-insensitive isoform of serine acetyltransferase from tobacco, i.e., NtSAT4. Constitutive overexpression of NtSAT4 in Brassica napus resulted in the 2.6-fold–4-fold higher SAT activity in different subcellular compartment-specific lines. This higher SAT activity led to a 2.5-fold–3.5-fold higher steady-state level of free Cys and 2.2-fold–5.3-fold elevated level of GSH in leaves compared with nontransformed plants. Among the compartment-specific lines, the mitochondrial targeted NtSAT4 overexpressor line M-182 showed the highest levels of Cys (3.5-fold) and GSH (5.3-fold) compared with wild-type plants. Overexpression of NtSAT4 conferred a physiological advantage in terms of enhanced tolerance against oxidative stress with hydrogen peroxide and the heavy metal cadmium (Cd). The NtSAT4 overexpressor lines showed a significantly higher amount of iron (Fe) translocation from roots to shoots compared with nontransformed plants. Overall, these results suggest that overexpression of NtSAT4 is a promising approach to creating plants with tolerance to heavy metals and oxidative stress and, in addition, may potentially improve plant nutrition in terms of enhanced Fe translocation from roots to shoots. • NtSAT4 overexpression elevates Cys and GSH levels in subcellular compartment-specific manner. • The mitochondrial targeted overexpression of NtSAT4 produces the highest levels of Cys and GSH. • The engineered transgenic lines show enhanced stress tolerance against heavy metals and oxidative stress. • Elevated Cys and GSH in the transgenic lines results in enhanced Fe translocation from roots to shoots. [ABSTRACT FROM AUTHOR]