Effects Of ROS And Caspase-3-like On Aerenchyma Formation Of Potamogeton Perfoliatus

Potamogeton perfoliatus is a perennial submerged plant belonging to Potamogeton.Developed aerenchyma is formed in it's roots,stems and leaves to maintain the supply of oxygen required for metabolism because of the anoxic environment it lives.It is known that the formation of aerenchyma in submerged plant is the result of hypoxia-induced programmed cell death(PCD).But the aerenchyma development process of Potamogeton perfoliatus has not been studied,the mechanism ROS interaction with Caspase-like proteins in intricate signaling networks to regulate PCD is still unknown.In this experiment,submerged macrophyte Potamogeton perfoliatus was used as materials to research the aerenchyma development process of roots,stems and leaves in time and space via paraffin sectioning technology.Potamogeton perfoliatus was treated with DPI,AT and AC-DEVD-CHO to study the effects of ROS and Caspase-3-like on aerenchyma formation.The main results are as follows:The aerenchyma development process of Potamogeton perfoliatus were divided into four phases:solid phase,formation phase,expansion phase,and maturity phase.Root aerenchyma forms about 0.3 mm from the root apex and matures at about 5 mm.The porosity in four phases are 0.36%,3.28%,10.43%and 15.41%,respectively.Stem aerenchyma forms about 0.6 mm from the stem apex and matures at about 2.4 mm.The porosity in four phases are 0.54%,10.90%,27.61%,and 57.58%,respectively.Aerenchyma porosity in node is only about 3.62%.Leaf aerenchyma forms in the second to third neonatal leaves near the stem apex and only forms in the main vein.Close correlation was found between aerenchyma formation of Potamogeton perfoliatus and the production of reactive oxygen species.Formation of aerenchyma was found inhibited with the increase of ROS related enzyme activities and the decrease of H2O2 content when treated with reactive oxygen species inhibitor DPI.And the inhibitory effect was most obvious when the treatment concentration was about 1 ?mol/L,and the porosity at maturity in stem was only 15.99%,which was about 27.75%of CK.The formation of aerenchyma was promoted with the decrease of ROS related enzyme activities and the increase of H2O2 content when treated with reactive oxygen species inducer AT.And the stem porosity at maturity was about 64.70%under the treatment of 500?mol/L AT,which kept a 12.26%increase than CK.Therefore,the presence of ROS has a promoting effect on the formation of aerenchyma.Aerenchyma formation of Potamogeton perfoliatus showed a close relationship with Caspase-3-like protein activity as well.Stem aerenchyma porosity and Caspase-3-like protein activity were inhibited when treated with DPI.while stem aerenchyma porosity and Caspase-3-like protein activity were promoted when treated with AT.Indicating that Caspase-3-like protein activity showed a positive correlation with stem aerenchyma porosity.In addition,compared with the treatment group treated with DPI or AT solely,the cross-treatment of AC-DEVD-CHO and DPI or AT significantly reduced Caspase-3-like activity and inhibited the development of aerenchyma respectively.Therefore,Caspase-3-like plays an important role during the formation of Potamogeton perfoliatus aerenchyma mediated by ROS.