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Exogenous spermidine is enhancing tomato tolerance to salinity-alkalinity stress by regulating chloroplast antioxidant system and chlorophyll metabolism.

Li J, Hu L, Zhang L, Pan X, Hu X - BMC Plant Biol. (2015)

Bottom Line: These effects were more pronounced in seedlings of cultivar Zhongza No. 9 than cultivar Jinpengchaoguan.The effect occurred earlier in cultivar Jinpengchaoguan than in cultivar Zhongza No. 9.Exogenous spermidine also exerts positive effects at the transcription level, such as down-regulation of the expression of the chlorophyllase gene and up-regulation of the expression of the porphobilinogen deaminase gene.

View Article: PubMed Central - PubMed

Affiliation: College of Horticulture, Northwest A&F University, Yangling, 712100, Shaanxi, China. lijianming66@163.com.

ABSTRACT

Background: Salinity-alkalinity stress is known to adversely affect a variety of processes in plants, thus inhibiting growth and decreasing crop yield. Polyamines protect plants against a variety of environmental stresses. However, whether exogenous spermidine increases the tolerance of tomato seedlings via effects on chloroplast antioxidant enzymes and chlorophyll metabolism is unknown. In this study, we examined the effect of exogenous spermidine on chlorophyll synthesis and degradation pathway intermediates and related enzyme activities, as well as chloroplast ultrastructure, gene expression, and antioxidants in salinity-alkalinity-stressed tomato seedlings.

Results: Salinity-alkalinity stress disrupted chlorophyll metabolism and hindered uroorphyrinogen III conversion to protoporphyrin IX. These effects were more pronounced in seedlings of cultivar Zhongza No. 9 than cultivar Jinpengchaoguan. Under salinity-alkalinity stress, exogenous spermidine alleviated decreases in the contents of total chlorophyll and chlorophyll a and b in seedlings of both cultivars following 4 days of stress. With extended stress, exogenous spermidine reduced the accumulation of δ-aminolevulinic acid, porphobilinogen, and uroorphyrinogen III and increased the levels of protoporphyrin IX, Mg-protoporphyrin IX, and protochlorophyllide, suggesting that spermidine promotes the conversion of uroorphyrinogen III to protoporphyrin IX. The effect occurred earlier in cultivar Jinpengchaoguan than in cultivar Zhongza No. 9. Exogenous spermidine also alleviated the stress-induced increases in malondialdehyde content, superoxide radical generation rate, chlorophyllase activity, and expression of the chlorophyllase gene and the stress-induced decreases in the activities of antioxidant enzymes, antioxidants, and expression of the porphobilinogen deaminase gene. In addition, exogenous spermidine stabilized the chloroplast ultrastructure in stressed tomato seedlings.

Conclusions: The tomato cultivars examined exhibited different capacities for responding to salinity-alkalinity stress. Exogenous spermidine triggers effective protection against damage induced by salinity-alkalinity stress in tomato seedlings, probably by maintaining chloroplast structural integrity and alleviating salinity-alkalinity-induced oxidative damage, most likely through regulation of chlorophyll metabolism and the enzymatic and non-enzymatic antioxidant systems in chloroplast. Exogenous spermidine also exerts positive effects at the transcription level, such as down-regulation of the expression of the chlorophyllase gene and up-regulation of the expression of the porphobilinogen deaminase gene.

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Related in: MedlinePlus

Effect of exogenous Spd on chlorophyll content in tomato seedlings. CK, 1/2 Hoagland’s solution; S, 75 mM saline–alkaline solution (NaCl: Na2SO4: NaHCO3: Na2CO3 = 1:9:9:1); SS, sprayed with 0.25 mM Spd and treated with 75 mM saline–alkaline solution. a, c and e represent cv. Zhongza No.9; (b, d and f) represent cv. Jinpengchaoguan
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Fig1: Effect of exogenous Spd on chlorophyll content in tomato seedlings. CK, 1/2 Hoagland’s solution; S, 75 mM saline–alkaline solution (NaCl: Na2SO4: NaHCO3: Na2CO3 = 1:9:9:1); SS, sprayed with 0.25 mM Spd and treated with 75 mM saline–alkaline solution. a, c and e represent cv. Zhongza No.9; (b, d and f) represent cv. Jinpengchaoguan

Mentions: As shown in Fig. 1, the contents of Chl a, Chl b and total Chl in salinity–alkalinity–stress (S)–treated two tomato cultivars increased early and decreased later, and peaked on fourth day, except for Chl b and total Chl contents in cv. Jinpengchaoguan (cv. JP) peaked on the second day. Compared with the control, the Chl content trended upward for 4 days after the initiation of salinity–alkalinity conditions, but then the levels declined and became significantly lower compared with CK–treated plants. During salinity–alkalinity stress, this trend was suppressed to some extent by salinity–alkalinity plus Spd (SS) treatment, as after 4 days of SS treatment, the decreases in Chl a, Chl b, and total Chl content in stressed seedlings of both cultivars were alleviated (Fig. 1).Fig. 1


Exogenous spermidine is enhancing tomato tolerance to salinity-alkalinity stress by regulating chloroplast antioxidant system and chlorophyll metabolism.

Li J, Hu L, Zhang L, Pan X, Hu X - BMC Plant Biol. (2015)

Effect of exogenous Spd on chlorophyll content in tomato seedlings. CK, 1/2 Hoagland’s solution; S, 75 mM saline–alkaline solution (NaCl: Na2SO4: NaHCO3: Na2CO3 = 1:9:9:1); SS, sprayed with 0.25 mM Spd and treated with 75 mM saline–alkaline solution. a, c and e represent cv. Zhongza No.9; (b, d and f) represent cv. Jinpengchaoguan
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4696305&req=5

Fig1: Effect of exogenous Spd on chlorophyll content in tomato seedlings. CK, 1/2 Hoagland’s solution; S, 75 mM saline–alkaline solution (NaCl: Na2SO4: NaHCO3: Na2CO3 = 1:9:9:1); SS, sprayed with 0.25 mM Spd and treated with 75 mM saline–alkaline solution. a, c and e represent cv. Zhongza No.9; (b, d and f) represent cv. Jinpengchaoguan
Mentions: As shown in Fig. 1, the contents of Chl a, Chl b and total Chl in salinity–alkalinity–stress (S)–treated two tomato cultivars increased early and decreased later, and peaked on fourth day, except for Chl b and total Chl contents in cv. Jinpengchaoguan (cv. JP) peaked on the second day. Compared with the control, the Chl content trended upward for 4 days after the initiation of salinity–alkalinity conditions, but then the levels declined and became significantly lower compared with CK–treated plants. During salinity–alkalinity stress, this trend was suppressed to some extent by salinity–alkalinity plus Spd (SS) treatment, as after 4 days of SS treatment, the decreases in Chl a, Chl b, and total Chl content in stressed seedlings of both cultivars were alleviated (Fig. 1).Fig. 1

Bottom Line: These effects were more pronounced in seedlings of cultivar Zhongza No. 9 than cultivar Jinpengchaoguan.The effect occurred earlier in cultivar Jinpengchaoguan than in cultivar Zhongza No. 9.Exogenous spermidine also exerts positive effects at the transcription level, such as down-regulation of the expression of the chlorophyllase gene and up-regulation of the expression of the porphobilinogen deaminase gene.

View Article: PubMed Central - PubMed

Affiliation: College of Horticulture, Northwest A&F University, Yangling, 712100, Shaanxi, China. lijianming66@163.com.

ABSTRACT

Background: Salinity-alkalinity stress is known to adversely affect a variety of processes in plants, thus inhibiting growth and decreasing crop yield. Polyamines protect plants against a variety of environmental stresses. However, whether exogenous spermidine increases the tolerance of tomato seedlings via effects on chloroplast antioxidant enzymes and chlorophyll metabolism is unknown. In this study, we examined the effect of exogenous spermidine on chlorophyll synthesis and degradation pathway intermediates and related enzyme activities, as well as chloroplast ultrastructure, gene expression, and antioxidants in salinity-alkalinity-stressed tomato seedlings.

Results: Salinity-alkalinity stress disrupted chlorophyll metabolism and hindered uroorphyrinogen III conversion to protoporphyrin IX. These effects were more pronounced in seedlings of cultivar Zhongza No. 9 than cultivar Jinpengchaoguan. Under salinity-alkalinity stress, exogenous spermidine alleviated decreases in the contents of total chlorophyll and chlorophyll a and b in seedlings of both cultivars following 4 days of stress. With extended stress, exogenous spermidine reduced the accumulation of δ-aminolevulinic acid, porphobilinogen, and uroorphyrinogen III and increased the levels of protoporphyrin IX, Mg-protoporphyrin IX, and protochlorophyllide, suggesting that spermidine promotes the conversion of uroorphyrinogen III to protoporphyrin IX. The effect occurred earlier in cultivar Jinpengchaoguan than in cultivar Zhongza No. 9. Exogenous spermidine also alleviated the stress-induced increases in malondialdehyde content, superoxide radical generation rate, chlorophyllase activity, and expression of the chlorophyllase gene and the stress-induced decreases in the activities of antioxidant enzymes, antioxidants, and expression of the porphobilinogen deaminase gene. In addition, exogenous spermidine stabilized the chloroplast ultrastructure in stressed tomato seedlings.

Conclusions: The tomato cultivars examined exhibited different capacities for responding to salinity-alkalinity stress. Exogenous spermidine triggers effective protection against damage induced by salinity-alkalinity stress in tomato seedlings, probably by maintaining chloroplast structural integrity and alleviating salinity-alkalinity-induced oxidative damage, most likely through regulation of chlorophyll metabolism and the enzymatic and non-enzymatic antioxidant systems in chloroplast. Exogenous spermidine also exerts positive effects at the transcription level, such as down-regulation of the expression of the chlorophyllase gene and up-regulation of the expression of the porphobilinogen deaminase gene.

Show MeSH
Related in: MedlinePlus