Morphology Of Starch Grains Research Articles

SUBSTANDARD STARCH GRAIN7 regulates starch grain size and endosperm development in rice.

Starch is synthesized as insoluble, semicrystalline particles within plant chloroplast and amyloplast, which are referred to as starch grains (SGs). The size and morphology of SGs in the cereal endosperm are diverse and species-specific, representing a key determinant of the suitability of starch for industrial applications. However, the molecular mechanisms modulating SG size in cereal endosperm remain elusive. Here, we functionally characterized the rice (Oryza sativa) mutant substandard starch grain7 (ssg7), which exhibits enlarged SGs and defective endosperm development. SSG7 encodes a plant-specific DUF1001 domain-containing protein homologous to Arabidopsis (Arabidopsis thaliana) CRUMPLED LEAF (AtCRL). SSG7 localizes to the amyloplast membrane in developing endosperm. Several lines of evidence suggest that SSG7 functions together with SSG4 and SSG6, known as two regulators essential for SG development, to control SG size, by interacting with translocon-associated components, which unveils a molecular link between SG development and protein import. Genetically, SSG7 acts synergistically with SSG4 and appears to be functional redundancy with SSG6 in modulating SG size and endosperm development. Collectively, our findings uncover a multimeric functional protein complex involved in SG development in rice. SSG7 represents a promising target gene for the biotechnological modification of SG size, particularly for breeding programs aimed at improving starch quality.

Morphology of starch grains of cassava cultivars (Manihot esculenta Crantz, Euphorbiaceae) – Pará, Brazil

Cassava (Manihot esculenta Crantz, Euphorbiaceae) is a species widely grown in Brazil, mainly by traditional communities of the Amazon, the cassava plots being home to a large number of cultivars yet to be investigated. This study aimed to characterize the morphology of starch grains found in the roots of five cultivars of cassava, coming from the Caxiuanã National Forest, Pará, Brazil, to verify the similarity among them. The starch grains were measured, described and illustrated in light microscopy and scanning electron microscopy. They were found to be smooth surfaced, non-compound, presenting miter, cup and rounded forms. Although the morphologies of the starch grains were quite similar among the cultivars studied, the statistical treatment applied showed significant differences in diameter, allowing the five cultivars to be narrowed down to only four.

What starch grain is that? – A geometric morphometric approach to determining plant species origin

Many economically important plants produce starch grains that, if distinctive in form, can be used as identifiers for particular taxa. The identification of starch to species or genera has become increasingly important in studies exploring plant use in ancient societies and also in the verification of plant origin for some plant-based medicines. However, identification of starch can be problematic, because of the considerable variability in the morphology of starch grains. As a result there has always been an element of subjective judgement when it comes to identifying a sample of grains. Here we present a novel system for identifying the plant species origin of unknown starch grains using image analysis of light micrographs. After manually obtaining a mask of the two-dimensional maximum-projection-area grain shape, features for each starch grain were determined automatically including the size metrics, circularity and Fourier transform signature. The starch grain features analysed were used to create classifiers for the grains. The relative performance of the different classifiers was evaluated, based on different combinations of the predictor variables (e.g. area, perimeter etc.), and the optimal classifier determined. The method was applied to a database of 1032 grains representing 8 geographically co-located known economic plant species. A classification tree using shape metrics and the Fourier signature produced the best separations. The morphological features were sufficient to obtain a high level of accuracy in attributing individual starch grains to plant species. The method enables the creation of effective classifiers to undertake a quantitative evaluation of starch grain morphologies, thereby reducing the need for subjective qualitative determinations. The system provides a robust framework in which plant microfossils of unknown species origin can be compared with reference grains for effecting identifications. The method is potentially useful not just for starch, but other microfossils of morphometric interest.

Starch grain morphology of the seagrasses Halodule wrightii, Ruppia maritima, Syringodium filiforme, and Thalassia testudinum

Starch grains are a ubiquitous component of plants that have been used in tandem with phytoliths, pollen, and macrofossils to reconstruct past floral diversity. This tool has yet to be fully explored for aquatic plants, specifically seagrasses, which lack phytoliths and are rarely preserved as macrofossils or pollen. If starch grains in seagrasses are morphologically distinct, this method has the potential to improve seagrass identification in the fossil record in such cases where its starch is preserved (e.g. scratches and occlusal surfaces of tooth enamel from seagrass consumers). The goals of this study were twofold: (1) to determine if starch is present in seagrass material and (2) to assess how starch grain morphology differs between different seagrasses. This study focused on four abundant and ecologically distinct seagrasses from the Caribbean: Halodule wrightii, Ruppia maritima, Syringodium filiforme, and Thalassia testudinum. Starch grains were observed in all species except S. filiforme. Grains from H. wrightii are typically observed in side-on orientation, are sub-round to angular, and are fairly small (3-19 μm, end-on). Grains of R. maritima are small spherical grains (4–8 μm) that have a centric hilum and a straight extinction cross with a median angle between the arms of 90°. Grains from T. testudinum are large (9–31 μm, end-on), conical in side-on and round/sub-round in end-on orientation, have a slightly eccentric hilum with an obvious particle, and prominent lamellae. Visual assessment and comparative statistics demonstrate that the morphology of starch grains from T. testudinum, R. maritima, and H. wrightii are significantly different. With more extensive research, there is potential for the positive identification of starch grains from an unknown seagrass. The ability to identify seagrass from starch grains could facilitate the identification of seagrasses in the fossil record and supply information on seagrass evolution and distribution, climate effects on seagrass distribution, and the diets of seagrass consumers.

Evolution of succulent <i>Euphorbia,/i> as interpreted from latex composition

The morphology of starch grains and the gas-liquid chromatographic profile of triterpenes derived from latex of the nonarticulated laticifer of succulent African Euphorbia were examined for their applicability to interpret phylogenetic relationships of this genus. Several trends in starch grain morphology and triterpene composition were evident in the 38 examined taxa. Rod shaped grains, interpreted to be conservative, occurred in only a few taxa in several dwarf groups. Grains of osteoid shape prevailed in most taxa. Highly osteoid grains possessing lobed ends represented the most complex form and were present in some taxa endemic to Madagascar. Triterpene profiles which contained from 2 to 14 or more compounds were derived from all taxa. Each taxon possessed a characteristic profile, or identifying fingerprint. The composition of the profile differed quantitatively and qualitatively among taxa. Taxa with few triterpenes, tentatively interpreted as primitive, occurred in dwarf forms, whereas Madagascan taxa tended to possess high numbers of triterpenes reflective of specialization. This study supports the interpretation that laticifer starch grain morphology and triterpene composition, both gene mediated stable markers, can be employed to determine and correlate phylogenetic relationships between taxa of this complex genus.

Scanning electron microscopy of starch grains from latex of Euphorbia terracina and E. tirucalli

The morphology of starch grains isolated from the latex of 2 species of Euphorbia was compared by scanning electron microscopy. In E. terracina they are elongated and greater, in diameter at the midregion than at the tips while in E. tirucalli they are osteoid. Starch grains varied in size in both, species although in E. tirucalli the largest grains, which measured 49 μ, were approximately twice the length of those in E. terracina (27 μ).