Abstract
Desiccation tolerance is the ability of orthodox seeds to achieve equilibrium with atmospheric relative humidity and to survive in this state. Understanding how orthodox seeds respond to dehydration is important for improving quality and long-term storage of seeds under low temperature and drought stress conditions. Long-term storage of seeds is an artificial situation, because in most natural situations a seed that has been shed may not remain in a desiccated state for very long, and if dormant it may undergo repeated cycles of hydration. Different types of seeds are differentially sensitive to desiccation and this directly affects long-term storage. For these reasons, many researchers are investigating loss of desiccation tolerance during orthodox seed development to understand how it is acquired. In this study, the orthodox seed proteome response of Fraxinus mandshurica Rupr. to dehydration (to a relative water content of 10%, which mimics seed dehydration) was investigated under four different conditions viz. 20 °C; 20 °C with silica gel; 1 °C; and 1 °C after pretreatment with Ca2+. Proteins from seeds dehydrated under different conditions were extracted and separated by two-dimensional difference gel electrophoresis (2D-DIGE). A total of 2919 protein spots were detected, and high-resolution 2D-DIGE indicated there were 27 differentially expressed. Seven of these were identified using MALDI TOF/TOF mass spectrometry. Inferences from bioinformatics annotations of these proteins established the possible involvement of detoxifying enzymes, transport proteins, and nucleotide metabolism enzymes in response to dehydration. Of the seven differentially abundant proteins, the amounts of six were down-regulated and one was up-regulated. Also, a putative acyl-coenzyme A oxidase of the glyoxylate cycle increased in abundance. In particular, the presence of kinesin-1, a protein important for regulation and cargo interaction, was up-regulated in seeds exposed to low temperature dehydration. Kinesin-1 is present in all major lineages, but it is rarely detected in seed desiccation tolerance of woody species. These observations provide new insight into the proteome of seeds in deep dormancy under different desiccation conditions.
Highlights
IntroductionIt was found that the germination ability of dormancy-released F. mandshurica seeds was normal under low temperature conditions (1 °C), but germination ability was reduced significantly for seeds that had undergone dehydration in low temperature conditions prior to the germination experiments [1]
The sensitivity of 2D-DIGE, coupled with protein identification using MALDI TOF/TOF, has permitted the study of the dynamic proteome of dormancy-released F. mandshurica seeds dehydrated at a critical stage to 10% relative water content (RWC) and low temperature, thereby providing insight into the processes that lead to desiccation-induced damage
Kinesin-1 has been rarely found in wood seed plants, and this protein may play a role in the establishment of cell morphology and environmental adaptation strategies
Summary
It was found that the germination ability of dormancy-released F. mandshurica seeds was normal under low temperature conditions (1 °C), but germination ability was reduced significantly for seeds that had undergone dehydration in low temperature conditions prior to the germination experiments [1] This interesting phenomenon is associated with seed desiccation tolerance against a variety of stresses that cause water deficits in seed cells, in orthodox seeds. This study was aimed to identify the different proteins that accumulate or decline in abundance in response to different dehydration conditions, with a view to understanding the molecular and physiological mechanisms underlying desiccation tolerance in this species. In the present study, alterations in the proteome were investigated in response to desiccation (10% RWC) in dormancy-released F. mandshurica seeds under different dehydration conditions. The proteome was studied using two-dimensional difference gel electrophoresis (2D-DIGE) and proteins were identified by matrix-assisted laser desorption/ionization time of flight (MALDI TOF/TOF) mass spectrometry (MS)
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