Biology subjects

Ngai, Q. Y.

Publications and source records attributed to Ngai, Q. Y..

3 recordsLinked to original sources

bioRxiv2023

Modification of amyloplast size in wheat endosperm through mutation of PARC6 affects starch granule morphology

Starch granule morphology is a major factor determining the functional and nutritional properties of starch. Here, we reveal amyloplast structure plays an important role in starch granule morphogenesis in wheat endosperm. Wheat amyloplasts contain large discoid A-type granules and small spherical B-type granules. We isolated a mutant in durum wheat defective in the plastid division protein PARC6, which had increased plastid size in both leaves and endosperm. Endosperm amyloplasts of the mutant contained more A- and B-type granules than those of the wild type. In mature grains, the mutant had larger A- and B-type granules than the wild type, and its A-type granules had a highly aberrant, lobed surface. This defect in granule morphology was already evident at early stages of grain development, when granule size was identical between the mutant and the wild type, and occurred without obvious alterations in starch polymer structure and composition. Plant growth and photosynthetic efficiency, as well as the size, number and starch content of grains, were not affected in the Ttparc6 mutants despite the large changes in plastid size. Interestingly, mutation of the PARC6 paralog, ARC6, in durum wheat did not increase plastid or starch granule size. We suggest this is because TtPARC6 can complement disrupted TtARC6 function by interacting with PDV2, the outer plastid envelope protein that typically interacts with ARC6 to promote plastid division. We propose that amyloplast compartment size and available stromal volume play important roles in determining starch granule size, shape and number per amyloplast.

plant biology↗

bioRxiv2022

Stomatal density affects rice mesophyll cell size and shape and modulates a conserved pattern of cells through the leaf

The structure of the mesophyll influences how light, CO2 and water travels inside a leaf, affecting the rates of both photosynthesis and transpiration. Recent studies in wheat and Arabidopsis have shown that the structure of the mesophyll is influenced by the density and activity of stomata, consistent with the hypothesis that gas flow via stomata can modulate internal cell growth and separation to co-ordinate leaf structure and function. To investigate whether this also occurs in rice, a staple food crop for a large fraction of the worlds population, we examined mesophyll structure in rice mutants with altered stomatal density. Our data show that stomatal function modulates mesophyll structure in rice. Variation in the degree of mesophyll lobing made a major contribution to altered mesophyll structure, suggesting that modified leaf gas flux through stomata influences an aspect of cell shape directly linked to gas exchange capacity in rice. In addition, our analysis revealed a previously unreported underlying pattern in cell size, shape and axiality across layers of the rice mesophyll, which further investigation revealed is present in a range of rice species and cultivars. The potential origin and significance of this mesophyll patterning are discussed. HIGHLIGHTWe describe a previously unreported cellular pattern in rice leaves and show that it is modulated by stomata. These results shed new light on leaf structure and function.

plant biology↗

bioRxiv2022

AtFZL is required for correct starch granule morphology in Arabidopsis chloroplasts

The control of starch granule number and morphology in plastids is poorly understood. Here, we demonstrate that AtFZL, a protein involved in thylakoid membrane organisation, is required for correct starch granule morphology in Arabidopsis. Leaves of mutants lacking AtFZL had the same starch content as wild-type leaves, but their starch granules were smaller and had a distinct, uneven surface morphology. Most chloroplasts in the mutant were larger than those of the wild type. However, the difference in chloroplast size could not explain the difference in granule size and shape in the Atfzl mutants, since other mutants with larger chloroplasts than the wild type (arc mutants) had granules that were similar in size and shape to wild-type granules. As reported previously, the Atfzl mutant had aberrant thylakoid organisation. We found that this phenomenon was particularly pronounced in regions surrounding starch granules. The location of the thylakoid-bound granule initiation protein MFP1 was unaffected in the Atfzl mutant. We propose that AtFZL affects starch granule size and shape by influencing thylakoid organisation at the periphery of starch granules. Our results are consistent with an important role for thylakoid architecture in determining granule morphology.

plant biology↗