Regulatory Role of Burkholderia sp. GD17 in Rice Seedling’s Responses to Cadmium Stress

doi:10.13560/j.cnki.biotech.bull.1985.2021-0915

Abstract

Abstract:

This work is to explore the regulatory role of Burkholderia sp. GD17 in the response of rice to cadmium（Cd）stress,thus laying a foundation for reducing Cd accumulation and increasing the Cd-tolerance of rice plant. GD17-inoculated（+GD17）and non-inoculated plants with Cd addition were used as study material,and their physiological and biochemical parameters,and gene expression were analyzed. The number of GD17 reached 3.6×10⁶ CFU/g of fresh root at 5 d after inoculation,and maintained a certain size of the endophytic population during plant growth. Following exposure to Cd（20 and 40 mg/kg soil）for 20 d,the dry and fresh weights of the shoots and roots of GD17-innoculated（+GD17）plants significantly were higher than that of non-inoculated seedlings. There was no significant difference in Cd contents of the roots between +GD17 and non-inoculated rice plants,while Cd content in the +GD17 shoots was only 43% of that in the non-inoculated ones. The contents of malondialdehyde in the roots and leaves of shoots of +GD17 rice plants were the 78% and 64% of those in non-inoculated plants under Cd stress. The activity of superoxide dismutase markedly decreased in the +GD17 shoots than in the non-inoculated ones,but the activities of peroxidase and catalase increased. GD17 addition efficiently inhibited the damages from photosynthesis,such as reduced the decrease of total chlorophyll content,net photosynthetic rate and stomatal conductance,and the increase of the intercellular CO₂ concentration from Cd stress. The Cd-induced photosynthetic impairment and GD17-conferred restorative effect were also reflected on the changes of revealed by chlorophyll fluorescence parameters. The expressions of the genes related to Cd absorption,chelation,transport,and vacuolar sequestration presented a higher level in the roots of +GD17 plants than in non-inoculated ones. These data suggest that root inoculated with GD17 may systematically alleviate Cd damage to rice seedlings,and the involved mechanisms might be associated with reducing root-shoot transport of Cd,regulating antioxidant defense from Cd,preventing Cd-induced photosynthetic impairment,and increasing the expressions of Cd tolerance-related genes. This work provided a scientific basis for the potential application of GD17 strain in low-Cd rice production.

Key words: cadmium stress, Burkholderia, rice, oxidative stress, photosynthesis, chlorophyll fluorescence

ZU Guo-qiang, HU Zhe, WANG Qi, LI Guang-zhe, HAO Lin. Regulatory Role of Burkholderia sp. GD17 in Rice Seedling’s Responses to Cadmium Stress[J]. Biotechnology Bulletin, 2022, 38(4): 153-162.

Figures/Tables 7

Table 1 Primer sequences used for the analysis of gene expression

基因 Gene	基因ID Gene ID	功能 Function	引物序列 Primer sequence（5'-3'）	产物长度 Length/bp
ABCG5	Os03g0281900	介导Cd进入液泡 Transporter pumping Cd into vacuole	F：AGGAGGACCTTCTGTACCCG R：CAGCATGATCGGGTTGTGGA	245
HMA1	Os06g0690700	介导Cd进入液泡 Transporter pumping Cd into vacuole	F：CCGTAGCCTTCCCACTTGTC R：ACCGCCCTCCAATGAGTTTC	140
HMA3	Os07g0232900	介导Cd进入液泡 Transporter pumping Cd into vacuole	F：CTGGCTCTGGTGATGCTTGT R：CCCAACCAGATGGAACGAGT	219
MT1a	Os11g0704500	Cd络合和活性氧清除 Cd chelation and ROS scavenging	F：TGCGGAAAGAAGTACCCTGAC R：CCTCAAACTGCTGCGCCTTC	100
MT1c	Os12g0571100	Cd络合和活性氧清除 Cd chelation and ROS scavenging	F：ATGTCGTGCGGTGGAAGTT R：TTGCAGTAGTGGTGGTGGTG	109
NRAMP5	Os07g0257200	调节Cd的根-茎转运 Regulating Cd root-shoot transport	F：GGCCTCCAAAAATACGGGGT R：GCAAGAACAGATTGTGGGGC	217
PCS1	Os05g0415200	介导络合素-Cd复合物的形成 Mediating the formation of phytochelatin -Cd complex	F：TGGATGTCGCTCGCTTCAAA R：CATGAACCCCCTGAGAAGCC	107
PCS2	Os06g0102300	介导络合素-Cd复合物的形成 Mediating the formation of phytochelatin -Cd complex	F：GCAACTGGTCTACTCAGGGG R：GCTTTCATCTCTGCAACTCTGC	101

Fig. 1 Colonization efficiency of GD17 inside roots as indicated by colony-forming units（CFU） GD17 inoculation was performed during seed germination,CK was replaced with distilled water. The data were collected from three replicated experiments（n = 3）with 5 plants used in each batch of experiment,and represented as means ± SD. Bars with different lower-case letters indicate significant differences at P<0.05. The same below

Fig. 2 Effects of GD17 and（or）Cd stress on plant grow-th and Cd contents Twenty-day-old plants were evaluated. The data were collected from three replicated experiments（n=3）with 20 plants used in each batch of experiment,and represented as means ± SD. A and B：Fresh and dry weight of shoots. C and D：Fresh and dry weight of roots. E：Representative pictures showing the morphology of aboveground part. F and G：Cd contents in roots and shoots

Fig. 3 Effects of GD17 and（or）Cd stress on malondialde-hyde（MDA）content of plants,and activities of antioxidation enzymes A and B：Malondialdehyde contents in roots and shoots. C and D：Superoxide dismutase activity in roots and shoots. E and F：Peroxidase activity in roots and shoots. G and H：Catalase activity in roots and shoots

Fig. 4 Effects of GD17 and（or）Cd stress on photosynth-esis-related parameters A：Total chlorophyll content. B：Photosynthetic rate（Pn）. C：Stomatal conductance（Gs）. D：Intercellular CO2 concentration（Ci）

Fig. 5 Effects of GD17 and（or）Cd stress on chlorophyll fluorescence parameters Fv/Fm：Maximal photochemical efficiency of PSII. ФPSII：Actual photochemical efficiency of PSII. ETR：Electron transport rate. NPQ：Non-photochemical quenching of fluorescence

Fig. 6 Effects of GD17 and（or）Cd stress on the expres-sion of Cd tolerance-related genes in roots

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