Effects of heat stress on enzyme activities and transcript levels in developing maize kernels grown in culture

Duke, Edwin R.; Doehlert, Douglas C.

doi:10.1016/0098-8472(96)01004-0

Cited by 52 publications

(43 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Although AGP and soluble starch synthase activities were most negatively impacted by elevated temperature, Singletary et al (12) concluded that AGP is likely more important in the premature cessation of starch deposition. In agreement, Duke and Doehlert (22) monitored a number of starch synthetic enzymes and their transcripts in kernels developed at elevated temperatures. AGP activity was most sensitive to elevated temperatures.…”

mentioning

confidence: 71%

Enhanced stability of maize endosperm ADP-glucose pyrophosphorylase is gained through mutants that alter subunit interactions

Greene

Hannah

1998

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Temperature lability of ADP-glucose pyrophosphorylase (AGP; glucose-1-phosphate adenylyltransferase; ADP: ␣-D-glucose-1-phosphate adenylyltransferase, EC 2.7.7.27), a key starch biosynthetic enzyme, may play a significant role in the heat-induced loss in maize seed weight and yield. Here we report the isolation and characterization of heat-stable variants of maize endosperm AGP. Escherichia coli cells expressing wild type (WT) Shrunken2 (Sh2), and Brittle2 (Bt2) exhibit a reduced capacity to produce glycogen when grown at 42°C. Mutagenesis of Sh2 and coexpression with WT Bt2 led to the isolation of multiple mutants capable of synthesizing copious amounts of glycogen at this temperature. An increase in AGP stability was found in each of four mutants examined. Initial characterization revealed that the BT2 protein was elevated in two of these mutants. Yeast two-hybrid studies were conducted to determine whether the mutant SH2 proteins more efficiently recruit the BT2 subunit into tetramer assembly. These experiments showed that replacement of WT SH2 with the heat-stable SH2HS33 enhanced interaction between the SH2 and BT2 subunits. In agreement, density gradient centrifugation of heated and nonheated extracts from WT and one of the mutants, Sh2hs33, identified a greater propensity for heterotetramer dissociation in WT AGP. Sequencing of Sh2hs33 and several other mutants identified a His-to-Tyr mutation at amino acid position 333. Hence, a single point mutation in Sh2 can increase the stability of maize endosperm AGP through enhanced subunit interactions.Temperature stress is a major environmental factor that greatly reduces grain yield and seed weight in many cereal crops such as maize, wheat, and barley. Direct measurements (1-6) as well as historical and climatological studies (7,8) have shown that elevated temperatures decrease the duration of grain filling in maize and decrease seed weight. That the physiological processes of the maturing seed itself are adversely affected by heat stress is evident from studies of in vitro-developed maize kernels. While kernels cultured at 35°C assimilate sugars at normal or elevated rates (9), seed weight is dramatically reduced (10). Similar studies with wheat and barley are consistent with the hypothesis that transport of sucrose to the endosperm is not limiting under high temperature conditions (11-13). Rather, conversion of sugars to storage products is adversely affected.Because starch accounts for approximately 70% of cereal seed weight, the stressful environmental factors must impact on this biochemical pathway. In this regard, studies from organisms ranging from bacteria to plants point to the important and rate-limiting nature of the starch biosynthetic enzyme, ADP-glucose pyrophosphorylase (AGP; glucose-1-phosphate adenylyltransferase; ADP:␣-D-glucose-1-phosphate adenylytransferase, EC 2.7.7.27). Historically, AGP has received considerable attention because of its allosteric properties and its position as the first unique step in starch synthesis (reviewed i...

show abstract

mentioning

confidence: 71%

Enhanced stability of maize endosperm ADP-glucose pyrophosphorylase is gained through mutants that alter subunit interactions

Greene

Hannah

1998

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Extensive studies have been done on the effects of heat stress on the activities of enzymes involved in Suc-to-starch metabolism in cereals (Caley et al, 1990;Hawker and Jenner, 1993;Keeling et al, 1993;Jenner, 1994; Cheih and Jones, 1995;Duke and Doehlert, 1996;Wilhelm et al, 1999;Hurkman et al, 2003). A correlation of reduction in starch content with declines in SuSase and SSS activities in heat-treated grains has been reported in these studies.…”

mentioning

confidence: 84%

“…It cleaves a-1,4 bonds on both amylose and amylopectin molecules and reattaches the released glucan segments to the same or another glucan chain through the formation of a-1,6 linkages (Hurkman et al, 2003). Its activity is closely associated with the increase in starch content during the development of rice endosperm (Nakamura et al, 1989;Nakamura and Yuki, 1992).Extensive studies have been done on the effects of heat stress on the activities of enzymes involved in Suc-to-starch metabolism in cereals (Caley et al, 1990;Hawker and Jenner, 1993;Keeling et al, 1993;Jenner, 1994; Cheih and Jones, 1995;Duke and Doehlert, 1996;Wilhelm et al, 1999;Hurkman et al, 2003). A correlation of reduction in starch content with declines in SuSase and SSS activities in heat-treated grains has been reported in these studies.…”

mentioning

confidence: 99%

Activities of Key Enzymes in Sucrose-to-Starch Conversion in Wheat Grains Subjected to Water Deficit during Grain Filling

et al. 2004

View full text Add to dashboard Cite

This study tested the hypothesis that a controlled water deficit during grain filling of wheat (Triticum aestivum) could accelerate grain-filling rate through regulating the key enzymes involved in Suc-to-starch pathway in the grains. Two high lodgingresistant wheat cultivars were field grown. Well-watered and water-deficit (WD) treatments were imposed from 9 DPA until maturity. The WD promoted the reallocation of prefixed 14 C from the stems to grains, shortened the grain-filling period, and increased grain-filling rate or starch accumulation rate (SAR) in the grains. Activities of Suc synthase (SuSase), soluble starch synthase (SSS), and starch branching enzyme (SBE) in the grains were substantially enhanced by WD and positively correlated with the SAR. ADP Glc pyrophosphorylase activity was also enhanced in WD grains initially and correlated with SAR with a smaller coefficient. Activities of granule-bound starch synthase and soluble and insoluble acid invertase in the grains were less affected by WD. Abscisic acid (ABA) content in the grains was remarkably enhanced by WD and very significantly correlated with activities of SuSase, SSS, and SBE. Application of ABA on well-watered plants showed similar results as those by WD. Spraying with fluridone, an ABA synthesis inhibitor, had the opposite effect. The results suggest that increased grainfilling rate is mainly attributed to the enhanced sink activity by regulating key enzymes involved in Suc-to-starch conversion, especially SuSase, SSS, and SBE, in wheat grains when subjected to a mild water deficit during grain filling, and ABA plays a vital role in the regulation of this process.Starch in the endosperm of wheat (Triticum aestivum) is the major form of carbon reserves and comprises 65% to 75% of the final dry weight of the grain (Housley et al., 1981;Dale and Housley, 1986;Hurkman et al., 2003). Grain filling is therefore mainly a process of starch biosynthesis and accumulation. It is generally accepted that four enzymes may play a key role in this process: Suc synthase (SuSase; EC 2.4.1.13), ADP Glc pyrophosphorylase (AGPase; EC 2.7.7.27), starch synthase (StSase; EC 2.4.1.21), and starch branching enzyme (SBE; EC 2.4. 1.18;Hawker and Jenner, 1993; Ahmadi and Baker, 2001;Hurkman et al., 2003). SuSase catalyses the cleavage of Suc, the main transported form of assimilates in wheat plants (Fisher and Gifford, 1986), to form UDP-Glc and Fru, which is thought to be the first step in the Suc-to-starch conversion. Its activity is considered to be linked to sink strength in the developing rice (Oryza sativa) grain and tomato (Lycopersicon esculentum) fruit (Sun et al., 1992;Wang et al., 1993;Kato, 1995). AGPase produces ADP-Glc, the primer of the starch chain (Smith and Denyer, 1992), and is regarded as the rate-limiting enzyme in starch biosynthesis (Preiss, 1988). StSase, composed of both soluble and granule-bound isoforms, elongates the amylose and amylopectin chains (Déjardin et al., 1997). Soluble StSase (SSS) activity is reported to be positively correlate...

show abstract

“…On the other hand, the activities of SuSy, GBSS, ADPG-Ppase were similar over a temperature range of 15-45°C. In maize kernels cultured in vitro, only ADPG-Ppase showed a marked response to high temperature (Duke and Dohlert 1996). Furthermore, other reports indicated that starch accumulation and composition in rice endosperm were under the coordinated regulation of several enzymes (Kawasaki et al 1996;Ball et al 1998).…”

Section: Introductionmentioning

confidence: 97%

Temperature induced changes in the starch components and biosynthetic enzymes of two rice varieties

et al. 2005

View full text Add to dashboard Cite

The effects of temperature on starch and amylose accumulation, fine structure of amylopectin and activities of some enzymes related to starch synthesis in developing rice endosperms was examined. Two early indica rice varieties were used, differing in amylose concentration (AC, %), namely Jia 935 (low AC) and Jia 353 (high AC). The results showed that the effects of high temperature on AC and amylopectin fine structure were variety-dependent. High temperature caused a reduction in amylose concentration and an increase in the short chain (CL<22) proportion of amylopectin for Jia 935; while opposite was true for Jia 353. High temperature also reduced and increased the activity of granulebound starch synthase (GBSS) in Jia 935 and in Jia 353, respectively. This suggests that a change in the ratio of amylose/starch due to temperature was attributable to a change in GBSS activity. Moreover, obvious differences between the two rice varieties were detected in the activities of sucrose synthase (SuSy), ADP-glucose pyrophosphorylase (ADPG-Ppase), soluble starch synthase (SSS), starch branching enzyme (SBE), starch de-branching enzyme (SDBE) and starch phosphorylase (SPase) to high temperature. Accumulation rate of amylose was significantly and positively correlated with GBSS for Jia 935, but not for Jia 353. Amylose accumulation was also significantly and positively correlated with the activities of SDBE, SBE, ADPG-Ppase and SuSy for both varieties. The results suggest that the ratio of amylose to starch in rice endosperm is not only related to GBSS, but also affected by the activities of SDBE, SBE, ADPG-Ppase and SuSy.

show abstract

Effects of heat stress on enzyme activities and transcript levels in developing maize kernels grown in culture

Cited by 52 publications

References 29 publications

Enhanced stability of maize endosperm ADP-glucose pyrophosphorylase is gained through mutants that alter subunit interactions

Enhanced stability of maize endosperm ADP-glucose pyrophosphorylase is gained through mutants that alter subunit interactions

Activities of Key Enzymes in Sucrose-to-Starch Conversion in Wheat Grains Subjected to Water Deficit during Grain Filling

Temperature induced changes in the starch components and biosynthetic enzymes of two rice varieties

Contact Info

Product

Resources

About