DTA

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Tesi etd-09242019-115417

Type of thesis
Dottorato
Author
HAMEDEH, HAYTHAM
URN
etd-09242019-115417
Title
The Response of the oilseed crop Camelina sativa to Flooding
Scientific disciplinary sector
BIO/04
Course
SCIENZE AGRARIE E BIOTECNOLOGIE - Agrobiodiversity
Committee
relatore Prof. PERATA, PIERDOMENICO
Keywords
  • Camelina
  • Flooding
  • Gibberellin
  • growth
  • hypoxia
  • Oxygen
  • quiscent
Exam session start date
;
Availability
parziale
Abstract
The major challenge of this work consisted of characterization the response mechanism of the oilseed crop Camelina sativa to flooding stress by analyzing the morphologic response under submergence and what was noticed that Camelina favored the adoption of an escape-like strategy through the elongation of its vegetative tissues and this elongation is recognized as an effort to reach the water surface, and this morphological response induced direct effects on plants physiology and metabolism as the plant triggered the activation of the anaerobic fermentation allowing the reserves of carbohydrates to be driven towards pyruvate production to maintain a low but continuous supply of ATP to support the overgrowing organs under submergence<br>in order to modulate the response of Camelina to flooding, through the application of a well know plant growth regulator in plants, Paclobutrazol (PBZ), which inhibits directly the early steps of gibberellin biosynthesis. PBZ treatment on two-week old seedlings shortly before being exposed to submergence was able to induce a quiescent-like response even after 72 hours of submergence in dark. The growth-inhibition contributed to the control the deteriorating effects of submergence, as PBZ application led to a reduction in the ROS-mediated cell wall oxidation meaning that the quiescent-responding plants retained more viable cells under submergence in addition to boosting the chlorophyll levels which plays a significant role in protecting the photosystem II from degradation during the sudden exposure to elevated oxygen concentration and high levels of radiation when the floodwater subsides and consequently allowing higher rate of survival.<br>The second approach aimed to limit the growth under submergence by applying certain modification on an oxygen-sensing molecular switch developed by Iacopino et al. (2019) which was designed and engineered based upon the oxygen sensing mechanism in the animal kingdom.<br>The switch was modified to suit the aim of this project by replacing the bioluminescent gene with a transcription factor that has the ability to generate changes in the plant’s morphology and physiology in hypoxia-inducible manner, and based on the output the second chapter where the inhibition of skotomorphogenesis, a response that usually occurs in dark flooded environment, which allowed a better adaptation and improved tolerance to extended durations of submergence. The transcription factors to be used as response mediator are PIF4 and HY5.<br>By generating a phosphorylation-resistant version of PIF4 and the fusion of the EAR motif dominant repressor domain (SRDX) allowed the repression of growth under submergence proving the functionality and the responsiveness of the molecular switch to hypoxic conditions. However, the repression of hypocotyl growth under well aerated dark conditions suggests a leakage in the system which might be due to increased activity of the original version of PIF4 gene.<br>In a similar trend to the oxygen-dependent suppressed PIF4 activity, transgenic Camelina plants overexpressing HY5 were able to reduce their growth in both dark and submergence conditions and efficiently drive a better survival levels as compared to the wild-type population.<br>
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