The Function Of LeMAPKs A In The Abscission Of Tomato Pedicel Explants

Plant organ shedding is an effective mechanism for plants to cope with the outside environment (such as drought, salt stress, plant diseases and insect pests), or to give up the redundant organs that are no longer important. The complex signal transduction mechanism is formed in plants to regulate the floral organs. Research on floral organ abscission signal induced by ethylene is more in-depth in the model organism Arabidopsis thaliana. It has become clear that Arabidopsis floral organ abscission of signal transduction pathway is BOP�'AtlDA�' AtHAESA�' AtMKKK?�'AtMKK4/MKK5�'AtMPK3/MPK6�' Abscission. However, there is still a gap in the MAPK cascade signal pathway. Tomato is the model organism of solanaceous crops. It is more practical significance to study the floral organ abscission of tomato about on MAPK role. The main results of this study are as follows:1. Identified the LeMAPK family Class A involved in the flower organs shedding of tomatoMAPK phylogenetic tree of Arabidopsis and tomato was constructed. The genetic distance between AtMAPK3 and LeMAPK1, LeMAPK2; AtMAPK6 and LeMAPK3, is the shortest. They are the same class A of MAPK family. So we choose LeMAPKl, LeMAPK2 and LeMAPK3 as the research object to carry out the subsequent research work on the tomato flower organ shedding.In tomato pedicel abscission process, the relative expression of LeMAPK1 and LeMAPK2 genes under natural conditions was increased, calcium treatment could reduce the dropout rate and the relative expression of LeMAPK1 and LeMAPK2 was to a certain degree inhibited. Expression of LeMAPK3 gene in tomato pedicel abscission process was no obvious up-regulated. Under salt stress conditions, the LeMAPKl/2 gene plays an important role in the start stage (12 h), while LeMAPK3 plays a role in the late fall (24 h). The above results show that the MAPK cascade is involved in abscission of tomato pedicel explants. And under different conditions, the mode of action is different.2. MAPK cascade is involved in the floral organ shedding associated with endogenous hormones and cell wall degrading enzymesUsing blocking agent of MAPK kinase (MBA) investigated the mechanism of the MAPK cascade in the floral organs shedding of tomato flower. Blocking agent of MAPK kinase applied to drop the shedding rate and the growth rate was significantly lower than that of the control group at the beginning of 8 hours. Blocking agent influenced hormone level change in different parts (Distal、AZ and Proximal) during the process of tomato pedicel abscission, which can decrease the content of ABA and increase IAA regulated in a certain range, and the regulation of GA is relatively complex, which is both up-regulated and down regulated. Blocking agent influenced the activity of cell wall degrading enzyme, cellulase, polygalacturonic acid enzyme and pectin esterase (CMC, PG and PE) enzyme activity in abscission zone and the distal flower were highly suppressed, the pedicel of proximal have relatively little effect. The effects of MAPK on the flower organs were explained by the regulation of endogenous hormone contents and cell wall degrading enzyme activity.3. MAPK blocking agent has inhibitive effects on abscission of tomato flower organs induced by ethyleneEthylene can directly induce abscission of tomato in vitro pedicel. Under the combined action of ethylene and blocking agent of MAPK kinase, we found pedicel abscission rate, hormone and cell wall degrading enzyme activity curves are in between the MBA and ethylene treated. It suggests that blocking agent by adjusting the internal hormone levels influence cell wall degrading enzyme activity, thereby inhibiting ethylene accelerated shedding. There is interaction between ethylene and blocking agent, which is speculated that the two signal pathways of ethylene and MAPK in the process of floral organ shedding are cross, the specific mechanism of action remains to be further studied.4. LeMAPK1 regulates abscission of tomato pedicel explants by genetic transformation of LeMAPKs AThe experiment took Micro-Tom tomato as transgenic material. the exogenous hormone concentration conditions, types and combinations, which influenced the generation of callus, adventitious bud and adventitious root development were studied. The best medium was MS+2.0mg/LZR+0.5mg/LIAA+3% sucrose for callus and adventitious bud formation, the ideal medium induced adventitious rooting was 1/2MS+1.5% +0.2mg/LIBA+3% sucrose. Also on the binary vector pBI121 for expression vector, studied the Kanamycin (Kan) resistance sensitivity of transformed cells, determined the best adventitious bud resistance screening concentration of 100 mg/L kanamycin was studied.In this study, the role of LeMAPKs A were studied. And constructed the expression vector pBI121-LeMAPK1, pBI121-LeMAPK2 and pBI121-LeMAPK3.The mutants of LeMAPK1 and LeMAPK2 over expression were obtained by Agrobacterium EHA105 mediated, the expression of LeMAPK2 and LeMAPKl in the mutant strains were 2.3 and 2.5 times increase in the leaves. the mutant of LeMAPKl showed the phenotype of abscission.