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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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Root growth of soybean seedlings exposed to a low water potential. Wild type (WT) and BiP overexpressing (BiP-2 and BiP-4 lines) soybean seedlings were grown on MS solid medium in the absence (A) and presence of 1% PEG (B) for 4 weeks when the roots were photographed. In (C), the root dry weight of 4-week-old seedlings (WT and BiP-4) grown in MS medium supplemented with 1% (PEG1) or 2% PEG (PEG2) was measured. (D) Root length of plants exposed to a drying soil. Water stress conditions were imposed in wild-type and BiP-4 transgenic lines at the V3 developmental stage by withholding irrigation for 7 d. Root length was measured on day 7. I, normally irrigated; DS, drought-stressed plants. (E) Root dry weight of plants exposed to drought. Root dry weight was measured on the 9th day of water deprivation. Asterisks indicate significant differences at P ≤0.05.
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fig4: Root growth of soybean seedlings exposed to a low water potential. Wild type (WT) and BiP overexpressing (BiP-2 and BiP-4 lines) soybean seedlings were grown on MS solid medium in the absence (A) and presence of 1% PEG (B) for 4 weeks when the roots were photographed. In (C), the root dry weight of 4-week-old seedlings (WT and BiP-4) grown in MS medium supplemented with 1% (PEG1) or 2% PEG (PEG2) was measured. (D) Root length of plants exposed to a drying soil. Water stress conditions were imposed in wild-type and BiP-4 transgenic lines at the V3 developmental stage by withholding irrigation for 7 d. Root length was measured on day 7. I, normally irrigated; DS, drought-stressed plants. (E) Root dry weight of plants exposed to drought. Root dry weight was measured on the 9th day of water deprivation. Asterisks indicate significant differences at P ≤0.05.

Mentions: Under water stress conditions, the relative water content in BiP OE lines were maintained close to the levels in plants that were not subjected to drought stress (data not shown; Fig. 3B), suggesting that a stress avoidance mechanism could account, at least in part, for the apparent increase in water stress tolerance mediated by BiP. The reported data indicate that stomatal closure did not account for the water-stress tolerance in the BiP overexpressing lines. It is hypothesized that an adaptation in root growth might explain the drought tolerance. PEG was used for inducing a low ψw stress. In the absence of PEG, the seedlings of controls and BiP-overexpressing lines developed roots at similar growth rates (Fig. 4A). The inclusion of 1% or 2% PEG in the rooting medium resulted in a typical increase in root growth in wild-type seedlings (Fig. 4B, C). By contrast, treatment of OE seedlings with PEG did not alter significantly root morphology and root DW. Hence overexpression of BiP seemed to prevent the drought-induced increase in root growth.


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)

Root growth of soybean seedlings exposed to a low water potential. Wild type (WT) and BiP overexpressing (BiP-2 and BiP-4 lines) soybean seedlings were grown on MS solid medium in the absence (A) and presence of 1% PEG (B) for 4 weeks when the roots were photographed. In (C), the root dry weight of 4-week-old seedlings (WT and BiP-4) grown in MS medium supplemented with 1% (PEG1) or 2% PEG (PEG2) was measured. (D) Root length of plants exposed to a drying soil. Water stress conditions were imposed in wild-type and BiP-4 transgenic lines at the V3 developmental stage by withholding irrigation for 7 d. Root length was measured on day 7. I, normally irrigated; DS, drought-stressed plants. (E) Root dry weight of plants exposed to drought. Root dry weight was measured on the 9th day of water deprivation. Asterisks indicate significant differences at P ≤0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig4: Root growth of soybean seedlings exposed to a low water potential. Wild type (WT) and BiP overexpressing (BiP-2 and BiP-4 lines) soybean seedlings were grown on MS solid medium in the absence (A) and presence of 1% PEG (B) for 4 weeks when the roots were photographed. In (C), the root dry weight of 4-week-old seedlings (WT and BiP-4) grown in MS medium supplemented with 1% (PEG1) or 2% PEG (PEG2) was measured. (D) Root length of plants exposed to a drying soil. Water stress conditions were imposed in wild-type and BiP-4 transgenic lines at the V3 developmental stage by withholding irrigation for 7 d. Root length was measured on day 7. I, normally irrigated; DS, drought-stressed plants. (E) Root dry weight of plants exposed to drought. Root dry weight was measured on the 9th day of water deprivation. Asterisks indicate significant differences at P ≤0.05.
Mentions: Under water stress conditions, the relative water content in BiP OE lines were maintained close to the levels in plants that were not subjected to drought stress (data not shown; Fig. 3B), suggesting that a stress avoidance mechanism could account, at least in part, for the apparent increase in water stress tolerance mediated by BiP. The reported data indicate that stomatal closure did not account for the water-stress tolerance in the BiP overexpressing lines. It is hypothesized that an adaptation in root growth might explain the drought tolerance. PEG was used for inducing a low ψw stress. In the absence of PEG, the seedlings of controls and BiP-overexpressing lines developed roots at similar growth rates (Fig. 4A). The inclusion of 1% or 2% PEG in the rooting medium resulted in a typical increase in root growth in wild-type seedlings (Fig. 4B, C). By contrast, treatment of OE seedlings with PEG did not alter significantly root morphology and root DW. Hence overexpression of BiP seemed to prevent the drought-induced increase in root growth.

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