The Mechanism Of H₂S Affecting The Abscissioon Of Plant Organs

The abscission of plant organs is a very noteworthy agronomic trait,and also an important physiological process in the process of plant growth and development.The leaves,flowers,fruits and seeds of plants can all fall off.Under normal conditions,abscission is conducive to the plant body to get rid of its own necrotic tissues or organs,so as to maintain the normal development of the plant body.Timely and appropriate seed shedding is also conducive to the reproduction of the plant,while in actual production,too much or too little falling flowers and fruits will affect the crop yield.Therefore,people sometimes need to promote the occurrence of organ abscission,and sometimes need to suppress the abscission.The occurrence of abscission is divided into four steps:?1?The formation of abscission zone?AZ?;?2?Obtain the ability to respond to falling off signals by abscission zone cells;?3?Initiation of the abscission process;?4?The formation of a protection layer.The second step is the most complex step in the abscission process,but the molecular mechanism is still elusive.The appearance of the third gas signaling molecule hydrogen sulfide?H₂S?has aroused great enthusiasm for its research.H₂S not only plays a great role in the growth and development of animals,but also plays a role in the regulation of the growth and development of plants.Our preliminary work has shown that H₂S treatment can significantly delay the abscission of tomato pedicel,an interesting phenomenon that has attracted our attention.This makes us think that H₂S is likely to interact with endogenous hormones to regulate the ability of off-site acquisition in response to abscission signals.What is the specific regulation mode? We explored how the H₂S signal affects the shedding of plant organs by interacting with endogenous hormones through physiological,biochemical,molecular and genetic studies.The main results are as follows:1.H₂S treatment can significantly delay the abscission of tomatopediceles and petioles,and the delayed effect of H₂S on organ abscission has dose effect within a certain concentration range.At the same time,H₂S significantly inhibited the expression of cell wall degrading enzyme-related genes in pedicels and petioles,but did not directly affect their enzyme activity at the protein level.Further studies showed that H₂S also had a significant inhibitory effect on the abscission of rose petals and petioles and the dehiscence of lily anthers,indicating that H₂S had a universal inhibitory effect on organ abscission in plants.2.The application of H₂S scavenging agent accelerated the process of tomato petiole and pedicel abscission,and the yield of H₂S decreased gradually during the process of tomato petiole abscission.In order to explore the role of endogenous H₂S in the process of tomato pedicel and petiole abscission,we constructed the gene knockout transgenic plants of Sl OAS2 and Sl OAS4,which encoded the tomato hydrogen sulfide generating enzymes.And the offspring of these transgenic plants were preliminarily analyzed.3.To explore the relationships between H₂S and the endogenous hormone auxin and ethylene,the expression level changes of auxin and ethylene related genes in pedicels and petioles before and after H₂S treatment were detected.It was found that H₂S may change the sensitivity of AZ cells to ethylene by affecting the content of free auxin contents,which eventually leads to the inhibition of abscission.Analysis of the expression of auxin synthesis related gene showed that H₂S significantly activated the expression of To FZY3 gene in the distal and AZ parts of the pedicel,while inhibited To FZY4 expression along the whole pedicel.We used an auxin synthesis inhibitor to jointly treat tomato pedicel with H₂S,and the inhibition effect of H₂S on tomato pedicel abscission disappeared,further proving that H₂S may regulate pedicel abscission by affecting auxin synthesis.4.In order to further explore the role of auxin synthesis gene in the inhibition of H₂S to the process of abscission,we constructed the knockout mutant of To FZY3 gene based on the CRISPR/Cas9 technology.The transgenic plants have been obtained and preliminarily analyzed.In summary,in this study,we found that H₂S has an inhibitory effect on the abscission process of plant organs,and this effect may be achieved by affecting the local auxin synthesis and forming a new auxin concentration gradient in the pedicel.This study enriched the regulatory network of plant organ abscission and provided new experimental evidence for the analysis of the physiological function of H₂S.