Study on the Mechanism of Exogenous Selenium Pretreatment Alleviating Cadmium Toxicity in Brassica juncea var. tumida Tsen et Lee Seedlings

doi:10.13560/j.cnki.biotech.bull.1985.2025-1079

Abstract

Abstract:

Objective To clarify the mechanism of exogenous selenium (Se) pretreatment alleviating cadmium (Cd) toxicity in Brassica juncea var. tumida Tsen et Lee seedlings, and to provide a theoretical basis for the rational application of Se to ensure the safe cultivation of Brassica juncea var. tumida Tsen et Lee in Cd-contaminated soils. Method The dominant cultivar ‘Yonganxiaoye’ which is sensitive to Cd stress was used as the experimental material, and a hydroponic experiment was conducted with four treatments: CK, CK+Se, Cd, and Cd+Se, thus to study the effects of exogenous selenium on Cd accumulation and distribution, photosynthetic assimilation capacity, and antioxidant capacity of B. juncea var. tumida Tsen et Lee seedlings under Cd stress. Results Compared with CK, Cd stress treatment markedly inhibited the growth of B. juncea var. tumida Tsen et Lee seedlings, reduced the chlorophyll content and photosynthetic efficiency of the plants, decreased the antioxidant enzymes activities, and increased the Cd content in both root and leaf tissues to 45.06 and 72.30 times that of CK, respectively. Compared with Cd stress alone, exogenous Se pretreatment significantly promoted the growth of B. juncea var. tumida Tsen et Lee seedlings under Cd stress, increased the chlorophyll content, Pn, Fv/Fm, ΦPSII, ETR, and qP values of the plants, enhanced the activities of SOD and CAT, and increased the contents of ASA, GSH, total phenol, phytochelatin, and cysteine content, down-regulated the expression levels of Cd uptake and transport-related genes (IRT1, Nramp1, HMA2, and HMA3) to 46.85%‒70.33% of those treated by Cd stress alone, reduced Cd accumulation in both root and leaf tissues and increased the proportion of Cd content in the cytoderm. Conclusion Exogenous Se alleviates Cd toxicity in B. juncea var. tumida Tsen et Lee seedlings under Cd stress, mainly by improving the conversion efficiency of photosynthetic system, enhancing the antioxidant capacity,^{strengthening the Cd chelating capacity and compartmentalization, and down-regulating the Cd uptake and transport-related genes expression levels.}

Key words: Brassica juncea var. tumida Tsen et Lee, cadmium stress, selenium, cadmium toxicity, antioxidant capacity

MO Yan-ling, LIU Yuan-yuan, PEI Jia-ling, FAN Xiang-man, DENG Xing-lian, ZENG Jing, LIU Yi-hua. Study on the Mechanism of Exogenous Selenium Pretreatment Alleviating Cadmium Toxicity in Brassica juncea var. tumida Tsen et Lee Seedlings[J]. Biotechnology Bulletin, 2026, 42(6): 304-313.

Figures/Tables 9

Table 1 Primer sequences for quantitative real-time PCR analysis

基因 Gene	基因登录号 Gene accession number	正向引物 Forward primer sequence （5′‒3′）	反向引物 Reverse primer （5′‒3′）
Actin3	BjuA014894	GGCTACTCTTTCACCACGAC	GGATACCAGCATTCTCCATAC
IRT1	AY087095.1	TGGCATTCTTTTTCGCGGTG	GCCGAGCATGCATTGAGAAG
IRT2	BT025714.1	CTCGTCGACCTTCTGGCTAC	ACTTGGCGACGACAGACATT
Nramp1	AF165125.1	CCCCGAAGACCGTGCTAAAT	TACCCACCACGTTTCGTAGC
HMA2	NM119157.3	GAGGATGCCACATGGTTGGA	CTTTGGTACGGCGGAAGAGT
HMA3	DQ446885.1	AACCTCGACGCTATGCACAA	GCTTGCCACGTCATCATTGG
HMA4	BjuO003139	TTCCCCACAAGAATCGCTCC	CACTCGAACCTTCCACGTCA

Fig. 1 External morphology of Brassica juncea var. tumida Tsen et Lee seedlings under different treatment conditionsCK: Hoagland’s complete nutrient solution. CK+Se: Hoagland’s complete nutrient solution + Selenium pretreatment. Cd: Cadmium stress treatment. Cd+Se: Cadmium stress treatment + Selenium pretreatment. bar=1 cm. The same below

Table 2 Effect of exogenous selenium pretreatment on the growth of B. juncea var. tumida Tsen et Lee seedlings under cadmium stress

处理 Treatment	叶片数 Leaf number	株高 Plant height （cm）	根长 Root length （cm）	地上鲜重 Shoot fresh weight （g）	地下鲜重 Root fresh weight （g）	地上干重 Shoot dry weight （g）	地下干重 Root dry weight （g）
CK	6.56±0.53a	7.06±0.29a	19.19±0.45a	7.52±0.34a	0.64±0.05a	0.64±0.08a	0.05±0.01ab
CK+Se	6.67±0.50a	7.12±0.36a	19.79±1.53a	7.55±0.24a	0.65±0.04a	0.63±0.08a	0.05±0.00a
Cd	5.89±0.33b	4.22±0.30c	12.78±1.65b	4.37±0.26c	0.35±0.03c	0.25±0.02c	0.04±0.00c
Cd+Se	6.44±0.53a	6.26±0.31b	18.64±0.76a	6.53±0.29b	0.51±0.04b	0.36±0.02b	0.04±0.00bc

Fig. 2 Effects of exogenous selenium pretreatment on the chlorophyll content, photosynthetic parameters, and chlorophyll fluorescence parameters of B. juncea var. tumida Tsen et Lee seedlings under cadmium stress

Fig. 3 Effects of exogenous selenium pretreatment on the MDA, H2O2, and O2- contents of B. juncea var. tumida Tsen et Lee seedlings under cadmium stress

Fig. 4 Effects of exogenous selenium pretreatment on the antioxidant enzyme activities and antioxidant contents of B. juncea var. tumida Tsen et Lee seedlings under cadmium stress

Fig. 5 Effects of exogenous selenium pretreatment on the chelating peptide and cysteinet contents of B. juncea var. tumida Tsen et Lee seedlings under cadmium stress

Fig. 6 Effects of exogenous selenium pretreatment on the cadmium accumulations of B. juncea var. tumida Tsen et Lee seedlings under cadmium stress

Fig. 7 Effects of exogenous selenium pretreatment on the expressions of genes related to cadmium uptake and transport in the roots of B. juncea var. tumida Tsen et Lee seedlings under cadmium stress

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