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The ER luminal binding protein (BiP) mediates an increase in drought tolerance in soybean and delays drought-induced leaf senescence in soybean and tobacco.

Valente MA, Faria JA, Soares-Ramos JR, Reis PA, Pinheiro GL, Piovesan ND, Morais AT, Menezes CC, Cano MA, Fietto LG, Loureiro ME, Aragão FJ, Fontes EP - J. Exp. Bot. (2008)

Bottom Line: When plants growing in soil were exposed to drought (by reducing or completely withholding watering) the wild-type lines showed a large decrease in leaf water potential and leaf wilting, but the leaves in the transgenic lines did not wilt and exhibited only a small decrease in water potential.It had previously been reported that tobacco BiP overexpression or repression reduced or accentuated the effects of drought.It is concluded that BiP overexpression confers resistance to drought, through an as yet unknown mechanism that is related to ER functioning.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Bioquímica e Biologia Molecular, BIOAGRO, Universidade Federal de Viçosa, Avenida PH Rolfs s/n, 36571.000 Viçosa, MG, Brazil.

ABSTRACT
The ER-resident molecular chaperone BiP (binding protein) was overexpressed in soybean. When plants growing in soil were exposed to drought (by reducing or completely withholding watering) the wild-type lines showed a large decrease in leaf water potential and leaf wilting, but the leaves in the transgenic lines did not wilt and exhibited only a small decrease in water potential. During exposure to drought the stomata of the transgenic lines did not close as much as in the wild type, and the rates of photosynthesis and transpiration became less inhibited than in the wild type. These parameters of drought resistance in the BiP overexpressing lines were not associated with a higher level of the osmolytes proline, sucrose, and glucose. It was also not associated with the typical drought-induced increase in root dry weight. Rather, at the end of the drought period, the BiP overexpressing lines had a lower level of the osmolytes and root weight than the wild type. The mRNA abundance of several typical drought-induced genes [NAC2, a seed maturation protein (SMP), a glutathione-S-transferase (GST), antiquitin, and protein disulphide isomerase 3 (PDI-3)] increased in the drought-stressed wild-type plants. Compared with the wild type, the increase in mRNA abundance of these genes was less (in some genes much less) in the BiP overexpressing lines that were exposed to drought. The effect of drought on leaf senescence was investigated in soybean and tobacco. It had previously been reported that tobacco BiP overexpression or repression reduced or accentuated the effects of drought. BiP overexpressing tobacco and soybean showed delayed leaf senescence during drought. BiP antisense tobacco plants, conversely, showed advanced leaf senescence. It is concluded that BiP overexpression confers resistance to drought, through an as yet unknown mechanism that is related to ER functioning. The delay in leaf senescence by BiP overexpression might relate to the absence of the response to drought.

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Induction of drought-responsive genes in transgenic lines. (A, B) Drought was induced in soybean plants at the V3 developmental stage by withholding irrigation for 7 d. Total RNA was isolated from leaves of wild type (WT) and 35S:BiP-4 lines and the transcript levels of selected genes (as indicated) were quantified by real-time PCR, using gene-specific primers. I, normally irrigated plants; DS, drought-stressed plants. Values represent the mean ±SD of three replicates. SMP, seed maturation protein; NAC2, transcription factor from the soybean NAC family; antqtn, antiquitin; GST, glutathione-S-transferase; PDI3, protein disulphide isomerase, isoform 3; BiPD, binding protein, isoform D from soybean; CNX, calnexin.
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fig6: Induction of drought-responsive genes in transgenic lines. (A, B) Drought was induced in soybean plants at the V3 developmental stage by withholding irrigation for 7 d. Total RNA was isolated from leaves of wild type (WT) and 35S:BiP-4 lines and the transcript levels of selected genes (as indicated) were quantified by real-time PCR, using gene-specific primers. I, normally irrigated plants; DS, drought-stressed plants. Values represent the mean ±SD of three replicates. SMP, seed maturation protein; NAC2, transcription factor from the soybean NAC family; antqtn, antiquitin; GST, glutathione-S-transferase; PDI3, protein disulphide isomerase, isoform 3; BiPD, binding protein, isoform D from soybean; CNX, calnexin.

Mentions: It was hypothesized that overexpression of BiP may indirectly affect stress tolerance by inducing a higher expression of water-stress responsive genes, such as SMP (seed maturation protein P30; AW397921; Irsigler et al., 2007), GST (glutathione-S-transferase; AAC18566; Irsigler et al., 2007), NAC2 (AY974350; Irsigler et al., 2007), PDI3 (protein disulphide isomerase, isoform 3; AW277660; Irsigler et al., 2007), and antiquitin (AY250704; Rodrigues et al., 2006). SMP is a marker gene for drought responses (Irsigler et al., 2007), GST participates in anti-oxidant reactions and detoxification (Dixon et al., 1998), and PDI is involved in protein folding, just as BiP (Kamauchi et al., 2008; Urade, 2007). NAC2 encodes a nuclear transfactor and antiquitin encodes a cytosolic aldehyde dehydrogenase. A large increase of the mRNA abundance of these genes was found in leaves of wild-type plants exposed to drought. Depending on the gene a smaller or a much smaller increase in mRNA abundance was observed in leaves of the BiP overexpressing plants (Fig. 6A). These results indicate that overexpression of BiP inhibits the induction of different classes of stress-responsive genes.


The ER luminal binding protein (BiP) mediates an increase in drought tolerance in soybean and delays drought-induced leaf senescence in soybean and tobacco.

Valente MA, Faria JA, Soares-Ramos JR, Reis PA, Pinheiro GL, Piovesan ND, Morais AT, Menezes CC, Cano MA, Fietto LG, Loureiro ME, Aragão FJ, Fontes EP - J. Exp. Bot. (2008)

Induction of drought-responsive genes in transgenic lines. (A, B) Drought was induced in soybean plants at the V3 developmental stage by withholding irrigation for 7 d. Total RNA was isolated from leaves of wild type (WT) and 35S:BiP-4 lines and the transcript levels of selected genes (as indicated) were quantified by real-time PCR, using gene-specific primers. I, normally irrigated plants; DS, drought-stressed plants. Values represent the mean ±SD of three replicates. SMP, seed maturation protein; NAC2, transcription factor from the soybean NAC family; antqtn, antiquitin; GST, glutathione-S-transferase; PDI3, protein disulphide isomerase, isoform 3; BiPD, binding protein, isoform D from soybean; CNX, calnexin.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2651463&req=5

fig6: Induction of drought-responsive genes in transgenic lines. (A, B) Drought was induced in soybean plants at the V3 developmental stage by withholding irrigation for 7 d. Total RNA was isolated from leaves of wild type (WT) and 35S:BiP-4 lines and the transcript levels of selected genes (as indicated) were quantified by real-time PCR, using gene-specific primers. I, normally irrigated plants; DS, drought-stressed plants. Values represent the mean ±SD of three replicates. SMP, seed maturation protein; NAC2, transcription factor from the soybean NAC family; antqtn, antiquitin; GST, glutathione-S-transferase; PDI3, protein disulphide isomerase, isoform 3; BiPD, binding protein, isoform D from soybean; CNX, calnexin.
Mentions: It was hypothesized that overexpression of BiP may indirectly affect stress tolerance by inducing a higher expression of water-stress responsive genes, such as SMP (seed maturation protein P30; AW397921; Irsigler et al., 2007), GST (glutathione-S-transferase; AAC18566; Irsigler et al., 2007), NAC2 (AY974350; Irsigler et al., 2007), PDI3 (protein disulphide isomerase, isoform 3; AW277660; Irsigler et al., 2007), and antiquitin (AY250704; Rodrigues et al., 2006). SMP is a marker gene for drought responses (Irsigler et al., 2007), GST participates in anti-oxidant reactions and detoxification (Dixon et al., 1998), and PDI is involved in protein folding, just as BiP (Kamauchi et al., 2008; Urade, 2007). NAC2 encodes a nuclear transfactor and antiquitin encodes a cytosolic aldehyde dehydrogenase. A large increase of the mRNA abundance of these genes was found in leaves of wild-type plants exposed to drought. Depending on the gene a smaller or a much smaller increase in mRNA abundance was observed in leaves of the BiP overexpressing plants (Fig. 6A). These results indicate that overexpression of BiP inhibits the induction of different classes of stress-responsive genes.

Bottom Line: When plants growing in soil were exposed to drought (by reducing or completely withholding watering) the wild-type lines showed a large decrease in leaf water potential and leaf wilting, but the leaves in the transgenic lines did not wilt and exhibited only a small decrease in water potential.It had previously been reported that tobacco BiP overexpression or repression reduced or accentuated the effects of drought.It is concluded that BiP overexpression confers resistance to drought, through an as yet unknown mechanism that is related to ER functioning.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Bioquímica e Biologia Molecular, BIOAGRO, Universidade Federal de Viçosa, Avenida PH Rolfs s/n, 36571.000 Viçosa, MG, Brazil.

ABSTRACT
The ER-resident molecular chaperone BiP (binding protein) was overexpressed in soybean. When plants growing in soil were exposed to drought (by reducing or completely withholding watering) the wild-type lines showed a large decrease in leaf water potential and leaf wilting, but the leaves in the transgenic lines did not wilt and exhibited only a small decrease in water potential. During exposure to drought the stomata of the transgenic lines did not close as much as in the wild type, and the rates of photosynthesis and transpiration became less inhibited than in the wild type. These parameters of drought resistance in the BiP overexpressing lines were not associated with a higher level of the osmolytes proline, sucrose, and glucose. It was also not associated with the typical drought-induced increase in root dry weight. Rather, at the end of the drought period, the BiP overexpressing lines had a lower level of the osmolytes and root weight than the wild type. The mRNA abundance of several typical drought-induced genes [NAC2, a seed maturation protein (SMP), a glutathione-S-transferase (GST), antiquitin, and protein disulphide isomerase 3 (PDI-3)] increased in the drought-stressed wild-type plants. Compared with the wild type, the increase in mRNA abundance of these genes was less (in some genes much less) in the BiP overexpressing lines that were exposed to drought. The effect of drought on leaf senescence was investigated in soybean and tobacco. It had previously been reported that tobacco BiP overexpression or repression reduced or accentuated the effects of drought. BiP overexpressing tobacco and soybean showed delayed leaf senescence during drought. BiP antisense tobacco plants, conversely, showed advanced leaf senescence. It is concluded that BiP overexpression confers resistance to drought, through an as yet unknown mechanism that is related to ER functioning. The delay in leaf senescence by BiP overexpression might relate to the absence of the response to drought.

Show MeSH
Related in: MedlinePlus