Heat Stress During Grain Filling in Maize: Effects on Carbohydrate Storage and Metabolism

1994 ◽  
Vol 21 (6) ◽  
pp. 829 ◽  
Author(s):  
GW Singletary ◽  
R Banisadr ◽  
PL Keeling
Keyword(s):  
Heat Stress ◽  
Seed Size ◽  
Starch Synthesis ◽  
Dry Weight ◽  
Grain Filling ◽  
Soluble Starch ◽  
Effect Of Temperature ◽  
Starch Accumulation ◽  
Maize Kernels

Heat stress during maize seed development can interfere with endosperm starch biosynthesis and reduce seed size, an important component of yield. Our objectives were to evaluate the direct influence of temperature during grain filling on kernel growth, carbohydrate accumulation, and corresponding endosperm metabolism. Kernels of maize were grown in vitro at 25�C until 15 or 16 days after pollination and then subjected to various temperatures for the remainder of their development. Mature kernel dry weight declined 45% in a linear fashion between 22 and 36�C. The rate of starch accumulation reached a maximum at approximately 32�C, and when measured at frequent intervals, declined only slightly with further temperature increase to 35�C. Reduced seed size resulted from an abbreviated duration of starch-related metabolism, which did not appear to be limited by endogenous sugars. Instead, a survey of 12 enzymes of sugar and starch metabolism indicated that ADP glucose pyrophosphorylase and soluble starch synthase were unique in displaying developmental peaks of activity which were compressed both in amount and time, similar to the effect of temperature on starch accumulation. We conclude that decreased starch synthesis in heat-stressed maize kernels results from a premature decline in the activity of these enzymes.

Effects of high temperature on grain growth and on the metabolites and enzymes in the starch-synthesis pathway in the grains of two wheat cultivars differing in their responses to temperature

2003 ◽  
Vol 30 (3) ◽  
pp. 291 ◽  
Author(s):  
Morteza Zahedi ◽  
Rajinder Sharma ◽  
Colin F. Jenner
Keyword(s):  
High Temperature ◽  
Starch Synthesis ◽  
Grain Filling ◽  
Triticum Aestivum L ◽  
Soluble Starch ◽  
Starch Synthase ◽  
Effect Of Temperature ◽  
The Difference

The effects of a sustained period of moderately high temperature were evaluated on the availability of substrate and the activity of starch synthase (ADP-glucose: 1,4-α-D-glucan 4-α-D-glucosyltransferase, EC 2.4.1.21) in the developing grains of two wheat Triticum aestivum L. cultivars differing in their tolerance to high temperature. Final grain weight was reduced by 33% in the least sensitive (cv. Kavko) and by 40% in the most sensitive (cv. Lyallpur) cultivar as post-anthesis temperature was raised from 20/15°C (day/night) to 30/25°C. The difference in the response of the two cultivars was mainly due to changes in the rate of grain filling at high temperature. The response of the rate of grain filling at high temperature, and the differential effects on the two cultivars, did not seem to be explained by an effect of temperature on the supply of assimilate (sucrose) or on the availability of the substrate for starch synthesis (ADP-glucose) in the grains. In vitro, but not in vivo, the differential responses of the efficiency (Vmax/Km) of soluble starch synthase in the two cultivars to an increase in temperature were associated with differences in the temperature sensitivity of grain filling. In vivo, the most remarkable difference between the two varieties was in the absolute values of the efficiency of soluble starch synthase, with the most tolerant cultivar having the highest efficiency.

scholarly journals Engineering 6-phosphogluconate dehydrogenase improves grain yield in heat-stressed maize

2020 ◽  
Vol 117 (52) ◽  
pp. 33177-33185
Author(s):  
Camila Ribeiro ◽  
Tracie A. Hennen-Bierwagen ◽  
Alan M. Myers ◽  
Kenneth Cline ◽  
A. Mark Settles
Keyword(s):  
Heat Stress ◽  
Grain Yield ◽  
Fusion Proteins ◽  
Starch Synthesis ◽  
Starch Accumulation ◽  
Chloroplast Targeting ◽  
Phosphogluconate Dehydrogenase ◽  
Heat Stable ◽  
Endosperm Starch

Endosperm starch synthesis is a primary determinant of grain yield and is sensitive to high-temperature stress. The maize chloroplast-localized 6-phosphogluconate dehydrogenase (6PGDH), PGD3, is critical for endosperm starch accumulation. Maize also has two cytosolic isozymes, PGD1 and PGD2, that are not required for kernel development. We found that cytosolic PGD1 and PGD2 isozymes have heat-stable activity, while amyloplast-localized PGD3 activity is labile under heat stress conditions. We targeted heat-stable 6PGDH to endosperm amyloplasts by fusing the Waxy1 chloroplast targeting the peptide coding sequence to the Pgd1 and Pgd2 open reading frames (ORFs). These WPGD1 and WPGD2 fusion proteins import into isolated chloroplasts, demonstrating a functional targeting sequence. Transgenic maize plants expressing WPGD1 and WPGD2 with an endosperm-specific promoter increased 6PGDH activity with enhanced heat stability in vitro. WPGD1 and WPGD2 transgenes complement the pgd3-defective kernel phenotype, indicating the fusion proteins are targeted to the amyloplast. In the field, the WPGD1 and WPGD2 transgenes can mitigate grain yield losses in high–nighttime-temperature conditions by increasing kernel number. These results provide insight into the subcellular distribution of metabolic activities in the endosperm and suggest the amyloplast pentose phosphate pathway is a heat-sensitive step in maize kernel metabolism that contributes to yield loss during heat stress.

High Temperature Affects the Activity of Enzymes in the Committed Pathway of Starch Synthesis in Developing Wheat Endosperm

1993 ◽  
Vol 20 (2) ◽  
pp. 197 ◽  
Author(s):  
JS Hawker ◽  
CF Jenner
Keyword(s):  
High Temperature ◽  
Sucrose Synthase ◽  
Starch Synthesis ◽  
Dry Weight ◽  
Grain Filling ◽  
Soluble Starch ◽  
Starch Synthase ◽  
Adpglucose Pyrophosphorylase ◽  
Udpglucose Pyrophosphorylase ◽  
Lower Temperature

Ears of wheat were exposed for up to 10 days during the grain-filling stage to high temperature (35�C) and activities of five enzymes in the sucrose to starch pathway were compared to those in ears maintained at lower temperature (21�C day/16�C night). Two cultivars of wheat known to differ in their post-anthesis tolerance of high temperature were compared. On a per grain basis, the activity of sucrose synthase and of ADPglucose pyrophosphorylase in ears maintained at 21/16�C throughout did not change greatly between days 16 and 32 after anthesis, whereas UDPglucose pyrophosphorylase and soluble starch synthase activities declined with advancing development. Soluble starch synthase activity in grains of heated ears was decreased within 1 day to about one- half of the value in unheated grains, and 3 days' additional heating did not reduce the activity much further. Insoluble starch synthase activity was not significantly reduced by heating. Compared to soluble starch synthase, ADPglucose pyrophosphorylase activity was more slowly affected and decreased to a lesser extent by heat. Sucrose synthase and UDPglucose pyrophosphorylase activities were either not affected or only slightly reduced; part of this reduction could be due to advanced development at the higher temperature. In recovery experiments ears were heated for brief periods and then returned to 21/16�C for a few days. ADPglucose pyrophosphorylase and soluble starch synthase activities recovered in the cooler conditions but the other two enzymes generally only maintained or lost further activity. From a comparison of the activities of these enzymes with the rate of starch deposition, and by taking into account the effects of heating, it is proposed that the influence of heating on final grain dry weight is attributable to the observed reductions of soluble starch synthase activity.

Effects of Temperature on the Conversion of Sucrose to Starch in the Developing Wheat Endosperm

1986 ◽  
Vol 13 (5) ◽  
pp. 605 ◽  
Author(s):  
SS Bhullar ◽  
CF Jenner
Keyword(s):  
Elevated Temperature ◽  
Starch Synthesis ◽  
Grain Filling ◽  
Residual Effects ◽  
Effect Of Temperature ◽  
Soluble Carbohydrate ◽  
Wheat Endosperm ◽  
14Co2 Production ◽  
Response To Temperature

Elevated temperature during grain filling resulted in reduced single grain weight due largely to an effect of temperature on the accumulation of starch in the endosperm. Wheat endosperm was cultured in vitro on solutions of [14C]sucrose and the responses to variation in temperature within the range 15-35°C were evaluated in terms of the absorption of radioactive sugar, the evolution of 14CO2, and the incorporation of radioactivity into starch. At 35°C the level of 14C in the intracellular pool of soluble carbohydrate was higher than it was at 30°C, and the average Q,10 for 14CO2 production was 2.1. Incorporation of 14C into starch was greater at 30°C than at 25°C, but at 35°C only half as much [14C]starch was produced compared with that at 30°C. Residual effects of exposure of ears to brief episodes of elevated temperature were investigated by culturing endosperm isolated from such ears on [14C]sucrose at a standard temperature (25°C). Two days of exposure resulted in greater amounts of [14C]starch produced, due to accelerated starch depo- sition, but longer periods (4-6 days) at elevated temperature resulted in substantial reductions in [14C]starch deposition. Exposure to elevated temperature also hastened the onset of chlorophyll degradation in the pericarp of the grain. Two types of response to temperature appear to be involved: a comparatively low temperature optimum for starch synthesis, and an irreversible reduction in the capacity of the endosperm to convert sucrose to starch resulting from exposure of the ears, or the grains themselves, to elevated temperature.

Starch Accumulation and Enzyme Activities Associated with Starch Synthesis in Maize Kernels

2007 ◽  
Vol 6 (7) ◽  
pp. 808-815 ◽  
Author(s):  
Hai-yan ZHANG ◽  
Shu-ting DONG ◽  
Rong-qi GAO ◽  
Qing-quan SUN
Keyword(s):  
Enzyme Activities ◽  
Starch Synthesis ◽  
Starch Accumulation ◽  
Maize Kernels

Starch Synthesis in the Kernel of Wheat Under High Temperature Conditions

1994 ◽  
Vol 21 (6) ◽  
pp. 791 ◽  
Author(s):  
CF Jenner
Keyword(s):  
High Temperature ◽  
Dry Matter ◽  
Starch Content ◽  
Starch Synthesis ◽  
Temperature Response ◽  
Grain Filling ◽  
Soluble Starch ◽  
Grain Weight ◽  
Temperature Range ◽  
Temperature Responses

As temperature rises above 18-22�C, the observed decrease in the duration of deposition of dry matter in the kernel is not accompanied by a compensating increase in the rate of grain filling with the result that grain weight (and yield) is diminished at high temperature. Reduced starch content accounts for most of the reduction in grain dry matter at high temperature. Responses to temperature in the low temperature range, 20-30�C (the LTR), could possibly be ascribed to the temperature response characteristics of the reaction catalysed by soluble starch synthase (SSS), the enzyme synthesising starch. However, the rate of cell enlargement and the rate of accumulation of nitrogen in the grain also do not increase much as temperature rises, so other explanations are conceivable for the temperature responses in the LTR. Variation amongst cultivars of wheat in tolerance of high temperature is evident in the LTR. At temperatures above 30�C (in the high temperature range (HTR) between 30 and 40�C), even for short periods, the rate of starch deposition is slower than that observed at lower temperatures, an effect which is carried over after transfer from high to lower temperatures. This response is attributable to a reduction in the activity, possibly due to thermal denaturation, of SSS. Several forms of SSS are found in cereal endosperm, and some forms may be more tolerant of high temperature than others. Loss of enzyme activity at high temperature is swift, but is partly restored some time after transfer from hot to cool conditions. There appear to be two distinct mechanisms of response to elevated temperature, both resulting in a reduced grain weight through reduced starch deposition, but one of them is important only in the range of temperature above 30�C.

scholarly journals Change in Sucrose Cleavage Pattern and Rapid Starch Accumulation Govern Lily Shoot-to-Bulblet Transition in vitro

2021 ◽  
Vol 11 ◽  
Author(s):  
Yun Wu ◽  
Ziming Ren ◽  
Cong Gao ◽  
Minyi Sun ◽  
Shiqi Li ◽  
...  
Keyword(s):  
Soluble Sugars ◽  
Starch Synthesis ◽  
Underlying Mechanism ◽  
Culture Conditions ◽  
Starch Accumulation ◽  
Cleavage Pattern ◽  
Additional Support ◽  
Clear Shift ◽  
Sucrose Cleavage

In bulb crops, bulbing is a key progress in micropropagation and is the feature that most distinguishes bulbous crops from other plants. Generally, bulbing involves a shoot-to-bulblet transition; however, the underlying mechanism remains elusive. We explored this process by tracking the shoot-to-bulblet transition under different culture conditions. Rapid starch accumulation occurred at 15 days after transplanting (DAT) in the bulblet-inducing treatments as confirmed via histological observations and the significant elevation of starch synthesis related-gene transcription, including LohAGPS, LohAGPL, LohGBSS, LohSS, and LohSBE. However, for shoots that did not transition to bulblets and maintained the shoot status, much higher soluble sugars were detected. Interestingly, we observed a clear shift from invertase-catalyzed to sucrose synthase-catalyzed sucrose cleavage pattern based on the differential expression of LohCWIN and LohSuSy during the key transition stage (prior to and after bulbing at 0–15 DAT). Shoots that transitioned into bulblets showed significantly higher LohSuSy expression, especially LohSuSy4 expression, than shoots that did not transition. A symplastic phloem unloading pathway at the bulblet emergence stage (15 DAT) was verified via the 6(5)-carboxyfluorescein diacetate fluorescent tracer. We propose that starch is the fundamental compound in the shoot-to-bulblet transition and that starch synthesis is likely triggered by the switch from apoplastic to symplastic sucrose unloading, which may be related to sucrose depletion. Furthermore, this study is the first to provide a complete inventory of the genes involved in starch metabolism based on our transcriptome data. Two of these genes, LohAGPS1.2b and LohSSIIId, were verified by rapid amplification of cDNA ends cloning, and these data will provide additional support for Lilium research since whole genome is currently lacking.

Activities of key enzymes involved in starch synthesis in grains of wheat under different irrigation patterns

2009 ◽  
Vol 147 (4) ◽  
pp. 437-444 ◽  
Author(s):  
Z. DAI ◽  
Y. YIN ◽  
Z. WANG
Keyword(s):  
Water Deficit ◽  
Enzyme Activities ◽  
Starch Synthesis ◽  
Grain Filling ◽  
Starch Accumulation ◽  
Wheat Cultivars ◽  
Wheat Grains ◽  
Key Enzymes ◽  
Grain Starch ◽  
Irrigation Patterns

SUMMARYIt is generally accepted that sucrose phosphate synthase (SPS), sucrose synthase (SuSy), ADP-glucose pyrophosphorylase (AGPase), soluble starch synthase (SSS), granule-bound starch synthase (GBSS) and starch branching enzyme (SBE) play a key role in starch synthesis in wheat grains. Starch synthesis in wheat grains is influenced by genotype and environment. However, what is not known is the degree of variation in enzyme activities during starch accumulation of wheat cultivars field-grown in different water regimes. The present study was undertaken to determine whether irrigation patterns could cause differences in starch accumulation and activities of key enzymes involved in starch synthesis. Starch accumulation and related enzyme activities were investigated in two winter wheat varieties, JM20 and BY535, differing in grain starch content, under two irrigation patterns. Results showed that soil water deficit led to an increase at early grain filling and decrease during late grain filling in starch accumulation rate (SAR) and activities of key enzymes involved in starch synthesis, especially AGPase, SSS and SBE. Water deficit enhanced grain starch accumulation in two wheat cultivars, suggesting that rainfed treatments increase physiological activities during early grain filling and promote starch accumulation. Furthermore, the change of SAR is consistent with SuSy, AGPase, SSS and GBSS. The results suggest that these enzymes play a key role in starch synthesis, and the decrease of photosynthate produced in the source organ is not the factor inhibiting starch accumulation.

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