Limits...
Salinity induces carbohydrate accumulation and sugar-regulated starch biosynthetic genes in tomato (Solanum lycopersicum L. cv. 'Micro-Tom') fruits in an ABA- and osmotic stress-independent manner.

Yin YG, Kobayashi Y, Sanuki A, Kondo S, Fukuda N, Ezura H, Sugaya S, Matsukura C - J. Exp. Bot. (2009)

Bottom Line: Tracer analysis with (13)C confirmed that elevated carbohydrate accumulation in fruits exposed to salinity stress was confined to the early development stages and did not occur after ripening.The results indicate that salinity stress enhanced carbohydrate accumulation as starch during the early development stages and it is responsible for the increase in soluble sugars in ripe fruit.These results indicate AgpL1 and AgpS1 are involved in the promotion of starch biosynthesis under the salinity stress in ABA- and osmotic stress-independent manners.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, Japan.

ABSTRACT
Salinity stress enhances sugar accumulation in tomato (Solanum lycopersicum) fruits. To elucidate the mechanisms underlying this phenomenon, the transport of carbohydrates into tomato fruits and the regulation of starch synthesis during fruit development in tomato plants cv. 'Micro-Tom' exposed to high levels of salinity stress were examined. Growth with 160 mM NaCl doubled starch accumulation in tomato fruits compared to control plants during the early stages of development, and soluble sugars increased as the fruit matured. Tracer analysis with (13)C confirmed that elevated carbohydrate accumulation in fruits exposed to salinity stress was confined to the early development stages and did not occur after ripening. Salinity stress also up-regulated sucrose transporter expression in source leaves and increased activity of ADP-glucose pyrophosphorylase (AGPase) in fruits during the early development stages. The results indicate that salinity stress enhanced carbohydrate accumulation as starch during the early development stages and it is responsible for the increase in soluble sugars in ripe fruit. Quantitative RT-PCR analyses of salinity-stressed plants showed that the AGPase-encoding genes, AgpL1 and AgpS1 were up-regulated in developing fruits, and AgpL1 was obviously up-regulated by sugar at the transcriptional level but not by abscisic acid and osmotic stress. These results indicate AgpL1 and AgpS1 are involved in the promotion of starch biosynthesis under the salinity stress in ABA- and osmotic stress-independent manners. These two genes are differentially regulated at the transcriptional level, and AgpL1 is suggested to play a regulatory role in this event.

Show MeSH
Change in 13C accumulation in developing fruits of plants grown under control and saline conditions. (A) Control (0 mM NaCl), (B) saline conditions (160 mM NaCl). Open and shaded columns indicate the time for sampling at 24 h and 48 h after feeding 13C-labelled carbon dioxide, respectively. (C) 13C accumulation in fruit per day calculated based on the mean values from (A) and (B). Open and shaded columns indicate control and salinity treatments. The horizontal axis indicates fruit developing stages. 10–14 DAF and 18–26 DAF correspond to the immature green and mature green stages, respectively. Values are means ±SD (n=3). The asterisks in (A) and (B) indicate statistical significance of the means in the same developing stage estimated using Fisher's PLSD test (*P <0.05, **P <0.01).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2803223&req=5

fig4: Change in 13C accumulation in developing fruits of plants grown under control and saline conditions. (A) Control (0 mM NaCl), (B) saline conditions (160 mM NaCl). Open and shaded columns indicate the time for sampling at 24 h and 48 h after feeding 13C-labelled carbon dioxide, respectively. (C) 13C accumulation in fruit per day calculated based on the mean values from (A) and (B). Open and shaded columns indicate control and salinity treatments. The horizontal axis indicates fruit developing stages. 10–14 DAF and 18–26 DAF correspond to the immature green and mature green stages, respectively. Values are means ±SD (n=3). The asterisks in (A) and (B) indicate statistical significance of the means in the same developing stage estimated using Fisher's PLSD test (*P <0.05, **P <0.01).

Mentions: To determine carbohydrate accumulation in the fruit during each development stage, tracer analysis was carried out with 13C-labelled carbon dioxide (Fig. 4). 13C taken up by control fruits increased from 3.12 mg g−1 DW at 24 h to 5.31 mg g−1 DW at 48 h after 13CO2 feeding in the fruits at 10–14 DAF (immature green), and from 1.13 mg g−1 DW at 24 h to 1.79 mg g−1 DW at 48 h in the fruits at 18–26 DAF (mature green) (Fig. 4A). On the other hand, 13CO2 taken up by salinity-stressed fruits increased from 1.69 mg g−1 DW at 24 h to 8.04 mg g−1 DW at 48 h in the fruits at 10–14 DAF, and from 0.79 mg g−1 DW at 24 h to 8.14 mg g−1 DW at 48 h in the fruits at 18–26 DAF (Fig. 4B). The increases in rate of 13C accumulation in fruit of the immature green and the mature green stages were 2.18 mg g−1 DW d−1 and 0.67 mg g−1 DW d−1 in the control fruit, 6.24 mg g−1 DW d−1, and 7.44 mg g−1 DW d−1 in salinity-stressed fruit. Carbon accumulation in the salinity-stressed fruit was 2.86 times higher in immature green and 11.1 times in mature green fruit than those into control fruit. In contrast to the early development stages of fruit, no active accumulation was observed after 34 DAF (yellow) in both conditions (Fig. 4C).


Salinity induces carbohydrate accumulation and sugar-regulated starch biosynthetic genes in tomato (Solanum lycopersicum L. cv. 'Micro-Tom') fruits in an ABA- and osmotic stress-independent manner.

Yin YG, Kobayashi Y, Sanuki A, Kondo S, Fukuda N, Ezura H, Sugaya S, Matsukura C - J. Exp. Bot. (2009)

Change in 13C accumulation in developing fruits of plants grown under control and saline conditions. (A) Control (0 mM NaCl), (B) saline conditions (160 mM NaCl). Open and shaded columns indicate the time for sampling at 24 h and 48 h after feeding 13C-labelled carbon dioxide, respectively. (C) 13C accumulation in fruit per day calculated based on the mean values from (A) and (B). Open and shaded columns indicate control and salinity treatments. The horizontal axis indicates fruit developing stages. 10–14 DAF and 18–26 DAF correspond to the immature green and mature green stages, respectively. Values are means ±SD (n=3). The asterisks in (A) and (B) indicate statistical significance of the means in the same developing stage estimated using Fisher's PLSD test (*P <0.05, **P <0.01).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2803223&req=5

fig4: Change in 13C accumulation in developing fruits of plants grown under control and saline conditions. (A) Control (0 mM NaCl), (B) saline conditions (160 mM NaCl). Open and shaded columns indicate the time for sampling at 24 h and 48 h after feeding 13C-labelled carbon dioxide, respectively. (C) 13C accumulation in fruit per day calculated based on the mean values from (A) and (B). Open and shaded columns indicate control and salinity treatments. The horizontal axis indicates fruit developing stages. 10–14 DAF and 18–26 DAF correspond to the immature green and mature green stages, respectively. Values are means ±SD (n=3). The asterisks in (A) and (B) indicate statistical significance of the means in the same developing stage estimated using Fisher's PLSD test (*P <0.05, **P <0.01).
Mentions: To determine carbohydrate accumulation in the fruit during each development stage, tracer analysis was carried out with 13C-labelled carbon dioxide (Fig. 4). 13C taken up by control fruits increased from 3.12 mg g−1 DW at 24 h to 5.31 mg g−1 DW at 48 h after 13CO2 feeding in the fruits at 10–14 DAF (immature green), and from 1.13 mg g−1 DW at 24 h to 1.79 mg g−1 DW at 48 h in the fruits at 18–26 DAF (mature green) (Fig. 4A). On the other hand, 13CO2 taken up by salinity-stressed fruits increased from 1.69 mg g−1 DW at 24 h to 8.04 mg g−1 DW at 48 h in the fruits at 10–14 DAF, and from 0.79 mg g−1 DW at 24 h to 8.14 mg g−1 DW at 48 h in the fruits at 18–26 DAF (Fig. 4B). The increases in rate of 13C accumulation in fruit of the immature green and the mature green stages were 2.18 mg g−1 DW d−1 and 0.67 mg g−1 DW d−1 in the control fruit, 6.24 mg g−1 DW d−1, and 7.44 mg g−1 DW d−1 in salinity-stressed fruit. Carbon accumulation in the salinity-stressed fruit was 2.86 times higher in immature green and 11.1 times in mature green fruit than those into control fruit. In contrast to the early development stages of fruit, no active accumulation was observed after 34 DAF (yellow) in both conditions (Fig. 4C).

Bottom Line: Tracer analysis with (13)C confirmed that elevated carbohydrate accumulation in fruits exposed to salinity stress was confined to the early development stages and did not occur after ripening.The results indicate that salinity stress enhanced carbohydrate accumulation as starch during the early development stages and it is responsible for the increase in soluble sugars in ripe fruit.These results indicate AgpL1 and AgpS1 are involved in the promotion of starch biosynthesis under the salinity stress in ABA- and osmotic stress-independent manners.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, Japan.

ABSTRACT
Salinity stress enhances sugar accumulation in tomato (Solanum lycopersicum) fruits. To elucidate the mechanisms underlying this phenomenon, the transport of carbohydrates into tomato fruits and the regulation of starch synthesis during fruit development in tomato plants cv. 'Micro-Tom' exposed to high levels of salinity stress were examined. Growth with 160 mM NaCl doubled starch accumulation in tomato fruits compared to control plants during the early stages of development, and soluble sugars increased as the fruit matured. Tracer analysis with (13)C confirmed that elevated carbohydrate accumulation in fruits exposed to salinity stress was confined to the early development stages and did not occur after ripening. Salinity stress also up-regulated sucrose transporter expression in source leaves and increased activity of ADP-glucose pyrophosphorylase (AGPase) in fruits during the early development stages. The results indicate that salinity stress enhanced carbohydrate accumulation as starch during the early development stages and it is responsible for the increase in soluble sugars in ripe fruit. Quantitative RT-PCR analyses of salinity-stressed plants showed that the AGPase-encoding genes, AgpL1 and AgpS1 were up-regulated in developing fruits, and AgpL1 was obviously up-regulated by sugar at the transcriptional level but not by abscisic acid and osmotic stress. These results indicate AgpL1 and AgpS1 are involved in the promotion of starch biosynthesis under the salinity stress in ABA- and osmotic stress-independent manners. These two genes are differentially regulated at the transcriptional level, and AgpL1 is suggested to play a regulatory role in this event.

Show MeSH