The Response Of CBF Cold Signaling Pathways For Banana Cold Resistance By Heat Treatment-induced And The Function By Disease-induced

Banana(Musa acuminata, AAA group) is one of the most important fruits and food crops in the tropical and subtropical regions. Postharvest banana is a kind of fruit that is sensitive to low temperature, which is easier to be damaged below 11?in the process of storage and transportation. Meanwhile, in this process, due to environment and other factors, it is susceptible to lead to latent bacteria by the colletotrichum gloeosporioides. Both above mentioned are seriously affected banana's appearance and its storage transportion, and also cause economic losses. Therefore,the study on chilling damage and disease resistance technology to banana as well as its mechanism has theoretical significance and application value.This paper makes use of banana(Musa. AAA group, cv. Brazil) trying to solve the problems that reduce banana's chilling damage and disease under the heat treatment(Hot water dipping, HWD) induction. It uses real-time PCR technology to detect gene expression level of cold signal, reactive oxygen species, calcium signaling,heat shock protein(HSP70) and heat shock transcription factor(HSFA1) after being heat treatment and being stored at temperature(20 ?) and low temperature(7 ?)condition respectively. This paper also researches chilling damage mechanism of postharvest banana after HWD, and analyzes the correlation among cold signaling pathway, reactive oxygen species, calcium signaling, HSP70, HSFA1. At last, it explores the relation of cold signaling pathway genes and disease stress during the storage.The research results are as follows:1. Through postharvest banana's HWD, MaICE gene expression induced by heat treatment at low temperature(7?) storage rise rapidly and reach its peak at 1h, the gene expression of DREB family(Ma DREB1 D ? Ma DREB1 E ? Ma DREB1 G and Ma DREB3) have a maximum peak at 1h under low temperature. Ma COR413 gene has a peak under low temperature after 4h. The pattern of Ma DREB1 D gene expression is different from other DREB family members on 1h and 120 h, which has a pesk under low temperature(7?) storage(highlighted of chilling injury symptom). In addition to,research shows that under low temperature, HWD improves its resistance after detecting banana's appearance picture, physiological index and cold signaling pathway genes, and also proves that postharvest banana does exist ICE-CBF-COR cold signaling pathway. And furthurmore, it is indicated that close connection between the possibility of postharvest banana's cold resistance after the HWD and CBF cold response pathway.2. Taking gene expression of reactive oxygen species after HWD and heatmap pattern analysis into consideration, under 20?storage conditions, HWD has a obvious inducement on Ma APX, Ma MAPK, Ma CAT, Ma NOX, and they have different degrees enhancement about gene expression.while it has not obvious cold resistance effect on Ma CAT, Ma NOX gene when they are stored at 7? low temperature. Meanwhile, it finds that its response time on HWD has similarities with expression time of cold signaling pathway ICE-CBF-COR. Therefore, it can be inferred that both reactive oxygen signal and cold signal pathway after HWD has the same response and their responses present up-regulation effect.3. After heat treatment, gene expression of Ma CA, Ma CMTA3 were induced under 20? storage, however, the gene expression showed a trend to decrease under the 7 ? storage, but it is generally higher than the control group; Ma Ca M and Ma CDPK gene after heat treatment-induced, the gene expression is up-regulation and higher than control group under 20? and 7? storage.Through analysis of gene expression of Ma CA ? Ma Ca M ? Ma CMTA3 ?Ma CDPK, being closely related to calcium signaling, it is indicated that after HWD they all have response on cold stress,when they are stored at 20? and 7?, and has the same trend to gene expression of cold signal pathway. In other word, gene expression level increased rapidly after HWD one to four hours and even at low temperature 7?, it also has a high response.Meanwhile they all have participation in the calcium signaling with regulation on cold stress. It can be inferred that due to HWD, calcium signaling pathway and cold signal pathway have the similar response, cross-regulatory network.4. Ma HSFA1, stored at low temperature 7?, its gene expression level gradually decreases. 52? HWD induced enhancement of Ma HSFA1 gene expression. and after HWD 0.5h, Ma HSFA1 reaches a little gene expression peak. During storage at low temperature(7 ?), Ma HSFA1 gene expression, treated by HWD at 4h, increased rapidly to a peak, and then decreased fast. In the whole process, HWD Ma HSFA1 gene expression is higher than control(except 7?120h) all the time. On account of storing at 7?, the gene expression of Ma HSP70 drops. Ma HSP70, after HWD 0.5h its gene expression increases rapidly to the maximum, four times than the control, and then decreases gradually. After the heat treatment, Ma HSP70 gene expression overall has a trend to drop at 7?storage, but it is still higher than the control. In general, cold resistance of postharvest banana by the HWD inducement, it may be closely related with Ma HSP70 and Ma HSFA1 gene expression.5. After HWD and inoculating banana anthracnose fungus(colletotrichum gloeosporioides), the possibility of the lesion and diease outbreak are both less than the control. It is incidated that HWD can improve the ability of postharvest banana disease resistance.Through the analysis of gene expression experiments on cold signaling pathway, postharvest banana fruit has been inoculated banana anthracnose fungus(colletotrichum gloeosporioides), Ma ICE gene expression decreases gradually,far lower than the control, It shows negative correlation with lesion size and infers that Ma ICE does not respond disease stress; while Ma DREB3 gene expression has no differrence with control, and indicates that Ma DREB3 does not respond to disease stress. However, there is a little indiction of inoculating banana anthracnose fungus on cold signaling pathway gene Ma DREB1 D, Ma DREB1 E, Ma DREB1 G, Ma COR413.Presumably, banana fruit disease and cold signaling pathway genes probably have some relevance.In summary, postharvest banana fruit, which is induced by the HWD, have the ICE-CBF-COR cold signaling pathway under low temperature. After the heat treatment-induced, CBF pathway gene expression rised rapidly within 0.5h, and it may be as an early response signal. Besides, it induced CBF pathway related gene expression to further enhanced and improved the cold resistance of banana fruit. CBF cold response pathway may play an important regulating role in the cold resistance of banana fruit by heat treatment-inducted. In addition, postharvest banana, with reactive oxygen species, calcium signaling, HSFA1, HSP70 makes up with mutual interrelated regulatory networks. Meanwhile, the induction effect of banana fruit, which is inoculated banana anthracnose fungus(colletotrichum gloeosporioides) on cold-signaling pathway genes is not obvious, but there has a little induction effect on some genes.