The role of transitory starch in C3, CAM, and C4 metabolism and opportunities for engineering leaf starch accumulation

AbstractDevelopment of the highly desiccation-sensitive (recalcitrant) seeds of primarily one species, Avicennia marina, is reviewed and compared with the ontogeny of desiccation-tolerant (orthodox) seeds. A. marina seeds undergo no maturation drying and remain metabolically active throughout development, which grades almost imperceptibly into germination. While PGR control of histodifferentiation is essentially similar to that characterizing desiccation-tolerant seeds, the phase of growth and reserve deposition is characterized by exceedingly high cytokinin levels which, it is proposed, promote a sink for assimilate import. While some starch accumulation does occur, the predominant reserves are soluble sugars which are readily available for the immediate onset of seedling establishment upon shedding. ABA levels are negligible in the embryo tissues during seed maturation, but increase in the pericarp, which imposes a constraint upon germination until these outer coverings are sloughed or otherwise removed. The pattern of proteins synthesized remains qualitatively similar throughout seed development in A. marina, and no LEA proteins are produced. This suggests both that seedling establishment is independent of maturation proteins and that the absence of LEAs and desiccation sensitivity might be causally related. The study on A. marina reveals that for this recalcitrant seed-type, germination per se cannot be defined: rather, it is considered as the continuation of development temporarily constrained by the pericarp ABA levels. This leads to a reexamination of the role of rehydration as key event sensu stricto, in the germination processes in desiccation-tolerant (orthodox) seeds.

Download Full-text

Starch branching enzymes as putative determinants of postharvest quality in horticultural crops

BMC Plant Biology ◽

10.1186/s12870-021-03253-6 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Jingwei Yu ◽

Keyun Wang ◽

Diane M. Beckles

Keyword(s):

Sugar Content ◽

Postharvest Quality ◽

Starch Accumulation ◽

Starch Degradation ◽

Published Data ◽

Horticultural Crops ◽

Starch Branching Enzymes ◽

Branching Enzymes ◽

End Use

AbstractStarch branching enzymes (SBEs) are key determinants of the structure and amount of the starch in plant organs, and as such, they have the capacity to influence plant growth, developmental, and fitness processes, and in addition, the industrial end-use of starch. However, little is known about the role of SBEs in determining starch structure-function relations in economically important horticultural crops such as fruit and leafy greens, many of which accumulate starch transiently. Further, a full understanding of the biological function of these types of starches is lacking. Because of this gap in knowledge, this minireview aims to provide an overview of SBEs in horticultural crops, to investigate the potential role of starch in determining postharvest quality. A systematic examination of SBE sequences in 43 diverse horticultural species, identified SBE1, 2 and 3 isoforms in all species examined except apple, olive, and Brassicaceae, which lacked SBE1, but had a duplicated SBE2. Among our findings after a comprehensive and critical review of published data, was that as apple, banana, and tomato fruits ripens, the ratio of the highly digestible amylopectin component of starch increases relative to the more digestion-resistant amylose fraction, with parallel increases in SBE2 transcription, fruit sugar content, and decreases in starch. It is tempting to speculate that during the ripening of these fruit when starch degradation occurs, there are rearrangements made to the structure of starch possibly via branching enzymes to increase starch digestibility to sugars. We propose that based on the known action of SBEs, and these observations, SBEs may affect produce quality, and shelf-life directly through starch accumulation, and indirectly, by altering sugar availability. Further studies where SBE activity is fine-tuned in these crops, can enrich our understanding of the role of starch across species and may improve horticulture postharvest quality.

Download Full-text

NaCl improves reproduction by enhancing starch accumulation in the ovules of the euhalophyte Suaeda salsa

10.21203/rs.2.23575/v3 ◽

2020 ◽

Author(s):

Jianrong Guo ◽

Ming Du ◽

Chaoxia Lu ◽

Baoshan Wang

Keyword(s):

Photosynthetic Efficiency ◽

Photochemical Efficiency ◽

Sucrose Phosphate Synthase ◽

Suaeda Salsa ◽

Starch Accumulation ◽

Photosynthetic Parameters ◽

Carbon Utilization ◽

Genes Encoding ◽

Sucrose Phosphate

Abstract Background: Halophytes show optimal reproduction under high-salinity conditions. However, the role of NaCl in reproduction and its possible mechanisms in the euhalophyte Suaeda salsa remain to be elucidated. Results: We performed transcript profiling of S. salsa flowers and measured starch accumulation in ovules, sugar contents in flowers, and photosynthetic parameters in the leaves of plants supplied with 0 and 200 mM NaCl. Starch accumulation in ovules, sugar contents in flowers and ovules, and net photosynthetic rate and photochemical efficiency in leaves were significantly higher in NaCl-treated plants vs. the control. We identified 14,348 differentially expressed genes in flowers of NaCl-treated vs. control plants. Many of these genes were predicted to be associated with photosynthesis, carbon utilization, and sugar and starch metabolism. These genes are crucial for maintaining photosystem structure, regulating electron transport, and improving photosynthetic efficiency in NaCl-treated plants. In addition, genes encoding fructokinase and sucrose phosphate synthase were upregulated in flowers of NaCl-treated plants. Conclusions: The higher starch and sugar contents in the ovules and flowers of S. salsa in response to NaCl treatment are likely due to the upregulation of genes involved in photosynthesis and carbohydrate metabolism, which increase photosynthetic efficiency and accumulation of photosynthetic products under these conditions.

Download Full-text

Role of calonyctin on free sugars in relation to starch accumulation in developing sweet potatoes

Journal of Plant Growth Regulation ◽

10.1007/bf00213131 ◽

1996 ◽

Vol 15 (1) ◽

pp. 27-31 ◽

Cited By ~ 2

Author(s):

S. -H. Shen ◽

H. -M. Shen ◽

J. -H. Wu

Keyword(s):

Starch Accumulation ◽

Sweet Potatoes ◽

Free Sugars

Download Full-text

Variation in carbon content and size in developing fruit of Actinidia deliciosa genotypes

Functional Plant Biology ◽

10.1071/fp09301 ◽

2010 ◽

Vol 37 (6) ◽

pp. 545 ◽

Cited By ~ 20

Author(s):

Simona Nardozza ◽

Helen L. Boldingh ◽

Annette C. Richardson ◽

Guglielmo Costa ◽

Hinga Marsh ◽

...

Keyword(s):

Organic Acids ◽

Fruit Development ◽

Soluble Sugars ◽

Seed Mass ◽

Actinidia Deliciosa ◽

Starch Accumulation ◽

Minor Role ◽

Dry Matter Content ◽

Final Composition

This study identifies the developmental processes contributing to variation in green-fleshed kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson var. deliciosa) fruit dry matter content (DM) and fresh weight (FW) by comparing genotypes with either high or low final DM. Results are compared with the model for fruit development, the tomato (Solanum lycopersicum L.). Differences in final composition were attributable to a higher rate of starch accumulation from 70 days after anthesis in high DM genotypes, with no other consistent differences in accumulation of soluble sugars or organic acids. High DM genotypes had 70% higher starch content and differed from low DM genotypes in the allocation of carbon between storage and other components. DM was negatively correlated with final fruit FW only in high DM genotypes, whereas starch was a constant proportion of dry weight (DW), suggesting a dilution effect rather than an interaction between fruit size and carbohydrate metabolism. Compared with tomato, the organic acids, particularly quinic acid, contributed more to estimated osmotic pressure during growth in FW than the soluble sugars, regardless of final composition or size. Seed mass per unit FW was highest in high DM genotypes, suggesting a previously unrecognised role for kiwifruit seeds in accumulation of carbohydrate by the pericarp. Anatomical comparisons also identified a role for differences in the packing of the two principal cell types, with an increased frequency of the larger cell type correlated with reduced DM. These genotypes demonstrate that kiwifruit differs from tomato in the role of starch as the principal stored carbohydrate, the reduced importance of dilution by growth in FW and the more minor role of the sugars compared with the organic acids during fruit development.

Download Full-text

Morpho-Physiological and Transcriptome Changes in Tomato Anthers of Different Developmental Stages under Drought Stress

Cells ◽

10.3390/cells10071809 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1809

Author(s):

Anthony Tumbeh Lamin-Samu ◽

Mohamed Farghal ◽

Muhammad Ali ◽

Gang Lu

Keyword(s):

Drought Stress ◽

Molecular Mechanisms ◽

Developmental Stages ◽

Soluble Sugars ◽

Anther Development ◽

Starch Accumulation ◽

Pollen Abortion ◽

Metabolic Genes ◽

Floral Bud

Drought limits the growth and productivity of plants. Reproductive development is sensitive to drought but the underlying physiological and molecular mechanisms remain unclear in tomatoes. Here, we investigated the effect of drought on tomato floral development using morpho-physiological and transcriptome analyses. Drought-induced male sterility through abnormal anther development includes pollen abortion, inadequate pollen starch accumulation and anther indehiscence which caused floral bud and opened flower abortions and reduced fruit set/yield. Under drought stress (DS), pollen mother cell to meiotic (PMC-MEI) anthers survived whereas tetrad to vacuolated uninucleate microspore (TED-VUM) anthers aborted. PMC-MEI anthers had lower ABA increase, reduced IAA and elevated sugar contents under DS relative to well-watered tomato plants. However, TED-VUM anthers had higher ABA increase and IAA levels, and lower accumulation of soluble sugars, indicating abnormal carbohydrate and hormone metabolisms when exposed to drought-stress conditions. Moreover, RNA-Seq analysis identified altogether >15,000 differentially expressed genes that were assigned to multiple pathways, suggesting that tomato anthers utilize complicated mechanisms to cope with drought. In particular, we found that tapetum development and ABA homeostasis genes were drought-induced while sugar utilization and IAA metabolic genes were drought-repressed in PMC-MEI anthers. Our results suggest an important role of phytohormones metabolisms in anther development under DS and provide novel insight into the molecular mechanism underlying drought resistance in tomatoes.

Download Full-text