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Germination and proteome analyses reveal intraspecific variation in seed dormancy regulation in common waterhemp (Amaranthus tuberculatus)
- Ramon G. Leon, Diane C. Bassham, Micheal D. K. Owen
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- Journal:
- Weed Science / Volume 54 / Issue 2 / April 2006
- Published online by Cambridge University Press:
- 20 January 2017, pp. 305-315
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Common waterhemp is an obligate outcrosser that has high genetic variability. However, under selection pressure, this weed shows population differentiation for adaptive traits. Intraspecific variation for herbicide resistance has been studied, but no studies have been conducted to determine the existence of variation for other adaptive traits that could influence weed management. The objective of this study was to examine the existence of different seed dormancy regulatory mechanisms in common waterhemp. Seed dormancy regulation, in response to different temperature and moisture regimes, was studied through germination experiments and proteome analysis using two common waterhemp biotypes (Ames and Everly) collected from agricultural fields in Iowa, and one biotype (Ohio) collected from a pristine area in Ohio. Without stratification, germination percentage among the different biotypes was 9, 29 and 88% for Ames, Everly, and Ohio respectively. The germination rate of seeds from Ames was dramatically increased after incubation at either 4 or 25 C under wet conditions, whereas germination of seeds from Everly was only increased at 25 C under wet conditions. The Ohio biotype showed no change in germination response to any of the incubation treatments. Germination studies indicated that the rate of seed dormancy alleviation differed between biotypes. Seed protein profiles obtained from the three biotypes differed in protein abundance, number, and type. A putative small heat-shock protein (sHSP) of 17.6 kDa and isoelectric point (pI) 6.1 increased whereas a putative glyceraldehyde-3-phosphate dehydrogenase (G3PDH) of 30.9 kDa and pI 6.4 decreased in abundance in the Ames biotype as seed dormancy was reduced in response to incubation at 4 C and wet conditions. These two proteins did not change in the Everly and Ohio biotypes, suggesting that these proteins changed their abundance in response to seed dormancy alleviation. The results of this study suggest that differences in seed dormancy levels between the biotypes were due to different physiological regulatory mechanisms.
Inheritance of deep seed dormancy and stratification-mediated dormancy alleviation in Amaranthus tuberculatus
- Ramon G. Leon, Diane C. Bassham, Micheal D.K. Owen
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- Journal:
- Seed Science Research / Volume 16 / Issue 3 / September 2006
- Published online by Cambridge University Press:
- 22 February 2007, pp. 193-202
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Amaranthus tuberculatus is a weed species that has shifted emergence patterns over the past few years, presumably due to changes in seed dormancy in response to selection in agricultural fields. Although it is recognized that the seed dormancy phenotype is greatly affected by the environment, it is also acknowledged that the genotype plays a significant role. However, the importance of the genotype in determining intra-population seed dormancy variability, and the effect on emergence patterns, is not well understood. The objective of the present study was to determine the importance of the genotype on deep dormancy and the stratification-mediated dormancy alleviation in A. tuberculatus. Wild populations differing in seed dormancy were crossed and F2 families were generated. These families were used to determine narrow sense heritability of dormancy and stratification-mediated dormancy alleviation at the individual (hi2) and family (hf2) levels. hi2 ranged from 0.13 to 0.4 and 0.04 to 0.06 for the dormancy and stratification response, respectively. In the case of hf2, the values ranged from 0.76 to 0.91 for deep dormancy and from 0.33 to 0.58 for the stratification response. The genetic correlation between these two traits was below 0.075, indicating that different genes control them. High temperature strengthened the dormancy of deeply dormant seeds, making them less sensitive to stratification. However, high temperature promoted the germination of non-deeply dormant seeds. It is proposed that delayed weed emergence can be generated by selecting genes that control stratification response, and not necessarily only the genes that are directly responsible for deep dormancy.
Transport of proteins into chloroplasts
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- By Julie W. Meadows, University of Warwick, Jamie B. Shackleton, University of Warwick, Diane C. Bassham, University of Warwick, Ruth M. Mould, University of Warwick, Andrew Hulford, University of Warwick, Colin Robinson, University of Warwick
- Edited by Alyson K. Tobin, University of Manchester
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- Book:
- Plant Organelles
- Published online:
- 05 December 2011
- Print publication:
- 15 October 1992, pp 281-292
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Summary
All cells transport proteins across membranes, but the complexity of protein traffic in plant cells is especially striking because of the variety of organelle types involved. Many proteins are inserted, during translation, into the lumen of the endoplasmic reticulum, after which they are transported via the endomembrane system to the Golgi apparatus, vacuole, protein bodies or plasma membrane. Other proteins are transported posttranslationally into glyoxysomes, mitochondria and plastids. In each case, the protein is synthesised with an appropriate signal which ensures targeting to the correct organelle, and a number of studies have attempted to define the characteristics of these targeting signals (reviewed by Bennett & Osteryoung, 1991; Robinson, 1991).
In terms of protein transport events, the biogenesis of the chloroplast is particularly complex, primarily owing to the architecture of the organelle. The chloroplast is bounded by a double-membrane envelope, between whose membranes is a soluble phase, the functions of which are presently obscure. Within the organelle is the soluble stromal phase (site of CO2 fixation, amino acid synthesis and many other key reactions) and the extensive internal thylakoid membrane. The thylakoid network also encloses a further soluble phase, usually termed the thylakoid lumen. Thus, the chloroplast comprises in total three distinct membranes and three discrete soluble phases. Most of the proteins located in each of these organellar compartments are encoded by nuclear genes, synthesised in the cytosol, and transported into the organelle. Clearly, therefore, chloroplast biogenesis requires both the specific, efficient targeting of a large number proteins into the organelle, and the operation of intraorganellar ‘sorting’ mechanisms to distribute imported proteins to their correct destinations.