(Starch synthesis in the maize endosperm as affected by starch-synthesizing mutants)

The goal of this work was to understand the role of the enzyme sucrose synthase (SuSy) in synthesis of cellulose and callose in plants. The work resulting from the this grant leads to a number of conclusions. SuSy clearly plays diverse roles in carbon metabolism. It can associate with the plasma membrane of cells undergoing rapid cellulose deposition, such as cotton fibers, developing maize endosperm, gravistimulated pulvini, and transfer cells of the cotton seed. It is also concentrated at sites of high callose deposition (tapetal cells; cell plates). When SuSy levels are lowered by mutation or by anti-sense technology, cell walls undergo degeneration (maize endosperm) and show reduced levels of cellulose (potato tubers). In sum, our evidence has very much strengthened the concept that SuSy does function in the plasma membrane to channel carbon from sucrose via UDP-glucose to glucan synthase complexes. Soluble SuSy also clearly plays a role in providing carbon for starch synthesis and respiration. Surprisingly, we found that the cotton seed is one unique case where SuSy apparently does not play a role in starch synthesis. Current evidence in sum suggests that no specific SuSy gene encodes the membrane-associated form, although in maize the SS 1 form of SuSy may be most important for cell wall synthesis in the early stages of endosperm development. Work is still in progress to determine what does control membrane localization - and the current evidence we have favors a role for Ca2+, and possibly also protein phosphorylation by differentially regulated protein kinases. Finally, we have discovered for the first time, a major new family of genes that encode the catalytic subunit of the cellulose synthase of plants - a result that has been widely cited and opens many new approaches for the study of this important plant function.

Download Full-text

Coordinated regulation of starch synthesis in maize endosperm by microRNAs and DNA methylation

The Plant Journal ◽

10.1111/tpj.15043 ◽

2020 ◽

Author(s):

Yufeng Hu ◽

Yangping Li ◽

Jianfeng Weng ◽

Hanmei Liu ◽

Guowu Yu ◽

...

Keyword(s):

Dna Methylation ◽

Starch Synthesis ◽

Maize Endosperm ◽

Coordinated Regulation

Download Full-text

Maize endosperm-specific transcription factors O2 and PBF network the regulation of protein and starch synthesis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1613721113 ◽

2016 ◽

Vol 113 (39) ◽

pp. 10842-10847 ◽

Cited By ~ 59

Author(s):

Zhiyong Zhang ◽

Xixi Zheng ◽

Jun Yang ◽

Joachim Messing ◽

Yongrui Wu

Keyword(s):

Transcription Factors ◽

Double Mutant ◽

Starch Content ◽

Starch Synthesis ◽

Starch Synthase ◽

Maize Endosperm ◽

Protein Levels ◽

Pyruvate Orthophosphate Dikinase ◽

Branching Enzymes ◽

Critical Components

The maize endosperm-specific transcription factors opaque2 (O2) and prolamine-box binding factor (PBF) regulate storage protein zein genes. We show that they also control starch synthesis. The starch content in the PbfRNAi and o2 mutants was reduced by ∼5% and 11%, respectively, compared with normal genotypes. In the double-mutant PbfRNAi;o2, starch was decreased by 25%. Transcriptome analysis reveals that >1,000 genes were affected in each of the two mutants and in the double mutant; these genes were mainly enriched in sugar and protein metabolism. Pyruvate orthophosphate dikinase 1 and 2 (PPDKs) and starch synthase III (SSIII) are critical components in the starch biosynthetic enzyme complex. The expression of PPDK1, PPDK2, and SSIII and their protein levels are further reduced in the double mutants as compared with the single mutants. When the promoters of these genes were analyzed, we found a prolamine box and an O2 box that can be additively transactivated by PBF and O2. Starch synthase IIa (SSIIa, encoding another starch synthase for amylopectin) and starch branching enzyme 1 (SBEI, encoding one of the two main starch branching enzymes) are not directly regulated by PBF and O2, but their protein levels are significantly decreased in the o2 mutant and are further decreased in the double mutant, indicating that o2 and PbfRNAi may affect the levels of some other transcription factor(s) or mRNA regulatory factor(s) that in turn would affect the transcript and protein levels of SSIIa and SBEI. These findings show that three important traits—nutritional quality, calories, and yield—are linked through the same transcription factors.

Download Full-text

ADP-glucose drives starch synthesis in isolated maize endosperm amyloplasts: characterization of starch synthesis and transport properties across the amyloplast envelope

Biochemical Journal ◽

10.1042/bj3240503 ◽

1997 ◽

Vol 324 (2) ◽

pp. 503-509 ◽

Cited By ~ 35

Author(s):

Torsten MÖHLMANN ◽

Joachim TJADEN ◽

Gundrun HENRICHS ◽

Paul W. QUICK ◽

Rainer HÄUSLER ◽

...

Keyword(s):

Starch Synthesis ◽

Dihydroxyacetone Phosphate ◽

Maize Endosperm ◽

Endosperm Tissue ◽

Plastid Envelope ◽

Phosphorylated Compounds ◽

Saturation Kinetics ◽

Uptake Data ◽

Hexose Phosphates

We recently developed a method of purifying amyloplasts from developing maize (Zea mays L.) endosperm tissue [Neuhaus, Thom, Batz and Scheibe (1993) Biochem. J. 296, 395–401]. In the present paper we analyse how glucose 6-phosphate (Glc6P) and other phosphorylated compounds enter the plastid compartment. Using a proteoliposome system in which the plastid envelope membrane proteins are functionally reconstituted, we demonstrate that this type of plastid is able to transport [14C]Glc6P or [32P]Pi in counter exchange with Pi, Glc6P, dihydroxyacetone phosphate and phosphoenolpyruvate. Glucose 1-phosphate, fructose 6-phosphate and ribose 5-phosphate do not act as substrates for counter exchange. Besides hexose phosphates, ADP-glucose (ADPGlc) also acts as a substrate for starch synthesis in isolated maize endosperm amyloplasts. This process exhibits saturation kinetics with increasing concentrations of exogenously supplied [14C]ADPGlc, reaching a maximum at 2 mM. Ultrasonication of isolated amyloplasts greatly reduces the rate of ADPGlc-dependent starch synthesis, indicating that the process is dependent on the intactness of the organelles. The plastid ATP/ADP transporter is not responsible for ADPGlc uptake. Data are presented that indicate that ADPGlc is transported by another translocator in counter exchange with AMP. To analyse the physiology of starch synthesis in more detail, we examined how Glc6P- and ADPGlc-dependent starch synthesis in isolated maize endosperm amyloplasts interact. Glc6P-dependent starch synthesis is not inhibited by increasing concentrations of ADPGlc. In contrast, the rate of ADPGlc-dependent starch synthesis is reduced by increasing concentrations of ATP necessary for Glc6P-dependent starch synthesis. The possible modes of inhibition of ADPGlc-dependent starch synthesis by ATP are discussed with respect to the stromal generation of AMP required for ADPGlc uptake.

Download Full-text

Identification of transcription factor ZmZAT8 involved in abscisic acid regulation pathway of starch synthesis in maize endosperm

Pakistan Journal of Botany ◽

10.30848/pjb2019-6(26) ◽

2019 ◽

Vol 51 (6) ◽

Cited By ~ 1

Author(s):

Tinglan Jiang ◽

Miao Xia ◽

Huanhuan Huang ◽

Jianlu Xiao ◽

Jiao Long ◽

...

Keyword(s):

Transcription Factor ◽

Abscisic Acid ◽

Starch Synthesis ◽

Maize Endosperm

Download Full-text

22KD Zein Content Coordinates Transcriptional Activity during Starch Synthesis in Maize Endosperm

Agronomy ◽

10.3390/agronomy10050624 ◽

2020 ◽

Vol 10 (5) ◽

pp. 624

Author(s):

Ada Menie Nelly Sandrine ◽

Hailiang Zhao ◽

Yao Qin ◽

Qin Sun ◽

Dianming Gong ◽

...

Keyword(s):

Sweet Corn ◽

Large Subunit ◽

Starch Synthesis ◽

Glycogen Metabolism ◽

Starch Accumulation ◽

Transferase Activity ◽

Maize Endosperm ◽

F2 Population ◽

Expression Of Genes ◽

Corn Inbred

Starch, the main form of stored energy in plants, plays an important role in maize (Zea mays L.) kernel development. The Shrunken-2 (Sh2) gene encodes the large subunit of the rate-limiting starch biosynthetic enzyme ADP-glucose pyrophosphorylase (AGPase). The sh2 mutant exhibits impaired AGPase activity, resulting in the partial or complete loss of starch synthesis. Here, we investigated the transcriptional regulatory framework of sh2 through transcriptome and co-expression network analysis using an F2 population derived from the maize reference line B73 and sweet corn inbred line HZ508. We identified 5175 differentially expressed genes (DEGs), including 2878 upregulated and 2297 downregulated genes in sh2 mutant lines. DEGs are associated with various biological processes including nutrient reservoir activity, transferase activity, catalytic activity, water deprivation and glycogen metabolism. At the genetic level, 2465 DEGs, including 357 transcription factors, were involved in transcription. In addition, the maize floury and opaque mutant genes fl1, ndk2, o7 and o2, which regulate the biosynthesis of 22KD zein, were co-expressed with the differential expressed transcription factor genes, thus suggesting that zein content might be a key regulator coordinating the expression of genes determining starch accumulation in maize endosperm.

Download Full-text

Transcription factor ZmPLATZ2 positively regulate the starch synthesis in maize

Plant Growth Regulation ◽

10.1007/s10725-020-00687-0 ◽

2021 ◽

Author(s):

Hui Li ◽

Yayun Wang ◽

Qianlin Xiao ◽

Li Luo ◽

Chunxia Zhang ◽

...

Keyword(s):

Transcription Factor ◽

Regulatory Mechanism ◽

Starch Synthesis ◽

Starch Synthase ◽

Rt Pcr ◽

Maize Endosperm ◽

Qrt Pcr ◽

Yield And Quality

AbstractMaize is one of the three major crops worldwide based on its yield and quality. Starch is crucial to both the yield and quality of maize as it accounts more than 60% of the seed weight, and its structure influences the quality of the crop. Starch synthase I (SSI) contributes to the majority of the starch synthase activity in the maize endosperm. An in-depth understanding of the starch synthesis regulatory mechanism would provide opportunities for improving the yield and quality of maize. In this study, ZmPLATZ2, a plant AT-rich sequence and zinc-binding protein (PLATZ) transcription factor related to starch synthesis, was selected based on co-expression analysis. The semiquantitative RT-PCR and qRT-PCR assays revealed that ZmPLATZ2 had a high expression in the endosperm, and reached the peak at 12 days after pollination (DAP). Different treatments demonstrated that ZmPLATZ2 was downregulated by the presence of sucrose. Subsequent transactivation and subcellular localization analyses showed that ZmPLATZ2 was localized in the nuclei without transactivation. Yeast one-hybrid and transient expression in maize endosperm indicated that ZmPLATZ2 could bind to the promoters of ZmSSI, ZmISA1, and ZmISA2 and increase their gene expression. After ZmPLATZ2 overexpression in rice, four starch synthesis genes were significantly upregulated in the transgenic plant, including the OsSSI gene. In vitro DAP-seq data showed that ZmPLATZ2 could bind to the CAAAAAAA element. In conclusion, our data support that ZmPLATZ2 binds to the CAAAAAAA element in the ZmSSI promoter and mediates the Glu signal pathway.

Download Full-text