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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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Drought-induced accumulation of some osmolytes in soybean transgenic lines. (A) Proline content in leaves of wild-type and 35S:BiP-4 transgenic lines under drought. Drought was induced in soybean plants at the V3 developmental stage by withholding irrigation for 7 d (DS) when the proline content of the leaves was determined. I denotes normally irrigated plants. (B, C) Soluble sugars content in leaves of wild type and independent transgenic lines (as indicated) cultivated under a restricted water regime. Drought stress (DS) conditions were imposed by reducing irrigation to a 40% level of the normal water supply for 18 d. I represents normally irrigated counterparts. After 18 d of treatment the leaf content of sucrose (B), and glucose (C) was measured. Asterisks indicate significant differences at P ≤0.05.
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fig5: Drought-induced accumulation of some osmolytes in soybean transgenic lines. (A) Proline content in leaves of wild-type and 35S:BiP-4 transgenic lines under drought. Drought was induced in soybean plants at the V3 developmental stage by withholding irrigation for 7 d (DS) when the proline content of the leaves was determined. I denotes normally irrigated plants. (B, C) Soluble sugars content in leaves of wild type and independent transgenic lines (as indicated) cultivated under a restricted water regime. Drought stress (DS) conditions were imposed by reducing irrigation to a 40% level of the normal water supply for 18 d. I represents normally irrigated counterparts. After 18 d of treatment the leaf content of sucrose (B), and glucose (C) was measured. Asterisks indicate significant differences at P ≤0.05.

Mentions: Proline is one of the major organic osmolytes that accumulates in a variety of plant species in response to drought, as a mechanism of dehydration avoidance (Porcel and Ruiz-Lozano, 2004; Ashraf and Foolad, 2007). Under drought conditions, both wild type and transgenic (35S:BiP-4) lines accumulated free proline in leaves to a higher level than their well-watered counterparts (Fig. 5A). Nevertheless, the proline level in stressed wild-type leaves was significantly greater than in stressed transgenic leaves. The soluble sugar content in leaves was also measured from independently transgenic lines as osmoprotectants (Porcel and Ruiz-Lozano, 2004). Water stress induced the accumulation of sucrose in wild-type leaves to a higher extent than in OE leaves and there were no clear differences between glucose levels of wild type and transgenic lines (Fig. 5B, C). These results indicated that changes in soluble sugars and proline levels were not associated with the high turgidity of transgenic leaves under drought.


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)

Drought-induced accumulation of some osmolytes in soybean transgenic lines. (A) Proline content in leaves of wild-type and 35S:BiP-4 transgenic lines under drought. Drought was induced in soybean plants at the V3 developmental stage by withholding irrigation for 7 d (DS) when the proline content of the leaves was determined. I denotes normally irrigated plants. (B, C) Soluble sugars content in leaves of wild type and independent transgenic lines (as indicated) cultivated under a restricted water regime. Drought stress (DS) conditions were imposed by reducing irrigation to a 40% level of the normal water supply for 18 d. I represents normally irrigated counterparts. After 18 d of treatment the leaf content of sucrose (B), and glucose (C) was measured. 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

fig5: Drought-induced accumulation of some osmolytes in soybean transgenic lines. (A) Proline content in leaves of wild-type and 35S:BiP-4 transgenic lines under drought. Drought was induced in soybean plants at the V3 developmental stage by withholding irrigation for 7 d (DS) when the proline content of the leaves was determined. I denotes normally irrigated plants. (B, C) Soluble sugars content in leaves of wild type and independent transgenic lines (as indicated) cultivated under a restricted water regime. Drought stress (DS) conditions were imposed by reducing irrigation to a 40% level of the normal water supply for 18 d. I represents normally irrigated counterparts. After 18 d of treatment the leaf content of sucrose (B), and glucose (C) was measured. Asterisks indicate significant differences at P ≤0.05.
Mentions: Proline is one of the major organic osmolytes that accumulates in a variety of plant species in response to drought, as a mechanism of dehydration avoidance (Porcel and Ruiz-Lozano, 2004; Ashraf and Foolad, 2007). Under drought conditions, both wild type and transgenic (35S:BiP-4) lines accumulated free proline in leaves to a higher level than their well-watered counterparts (Fig. 5A). Nevertheless, the proline level in stressed wild-type leaves was significantly greater than in stressed transgenic leaves. The soluble sugar content in leaves was also measured from independently transgenic lines as osmoprotectants (Porcel and Ruiz-Lozano, 2004). Water stress induced the accumulation of sucrose in wild-type leaves to a higher extent than in OE leaves and there were no clear differences between glucose levels of wild type and transgenic lines (Fig. 5B, C). These results indicated that changes in soluble sugars and proline levels were not associated with the high turgidity of transgenic leaves under drought.

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