Progress 09/01/05 to 02/28/09
Outputs
OUTPUTS: This study aims at genetically and biochemically identifying key genes involved in differential responses to two ambient temperatures 22C and 28C. We have achieved the goals set in the proposal First, we have identified marker genes for temperature responses and utilized them in further genetic dissection of temperature sensing and signaling. Second, we have characterized mutants defective in temperature modulation of defense responses and cloned two corresponding genes. Third, we have isolated cis-acting element conferring regulation of a temperature responsive gene BAP1 and identified its potential trans-acting factor. PARTICIPANTS: Ying Zhu, postdoc Huijung Yang, postdoc Yi Wang, graduate student TARGET AUDIENCES: scientific research community plant breeders PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
We have gained a better understanding of the regulation of temperature responses and temperature modulation of defense responses through these studies. The major findings are: 1. Transcriptional responses to extreme and non-extreme temperature variations use both distinct and shared signaling cascades. The CBF genes and the CRT/DRE element are used in cooling responses. 2. A cis-element responsive to a cooling induction is identified in the BAP1 promoter and ICE1 might be its trans-acting factor. 3. Temperature sensitive component in plant defense responses have been identified through mutant screens. 4. Heat-stable disease resistance has been generated through modifying the temperature sensitive component in Arabidopsis. 5. Preliminary results indicate that heat-stable resistance can also be generated in non-Arabidopsis plants using knowledge gained from Arabidopsis.
Publications
- Li Y, Yang S, Yang H, and Hua J. (2007) The TIR-NB-LRR gene SNC1 is regulated at the transcript level by multiple factors. MPMI 20,1449.
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Progress 09/01/06 to 08/31/07
Outputs
OUTPUTS: We have been continuing our study of regulation of temperature responses at the non-extreme ranges. We compared the molecular responses to extreme and non-extreme temperatures and dissected a promoter of temperature responsive gene. We have also characterized a number of mutants that are insensitive to temperature modulation of defenses and have cloned a few genes corresponding for these mutants through map-based cloning. In addition, these projects have provided training for three postdoctoral fellows, three graduate students and four undergraduate students. Scientific results from this research have been disseminated through seminars and publications.
PARTICIPANTS: Ying Zhu Yi Wang Huijun Yang
TARGET AUDIENCES: target audiences: research community and plant breeders efforts: education opportunities for undergraduate students
Impacts
We have gained a better understanding of the regulation of temperature responses. The major findings are: 1. Comparative study reveals both distinct and overlapping mechanisms for temperature responses at extreme and non-extreme ranges. 2. A CBF like factor is found to be involved in temperature responses at the non-extreme range. 3. Two heat-stable disease resistance mutants were identified and one corresponding gene has been cloned.
Publications
- Li Y, Yang S, Yang H, and Hua J. 2007. The TIR-NB-LRR gene SNC1 is regulated at the transcript level by multiple factors. MPMI 20,1449.
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Progress 09/01/05 to 09/01/06
Outputs
1. Comparative studies of transcriptional regulations by extreme and non-extreme temperatures. Several molecular markers were identified for temperature responses at the non-extreme range (between 16C and 28C). We found that temperature variations at extreme and non-extreme ranges regulate both overlapping and distinct sets of genes. We further analyzed the induction of the gene COR15a by cold (4C) and by cooling (28C to 22C) through a promoter deletion series. The DRE/CRT cis-element responsible for cold induction is also required for cooling induction. We are now using RNAi to knock down the CBF transcriptional factors to assess its impact on COR15a induction by cold and cooling. In addition, we found that salicylic acid is required for the cooling induction of EDS1 but not COR15a. Thus, both distinct and shared mechanisms are utilized by plants to respond to extreme and non-extreme temperatures and more than one signaling pathway is utilized to respond to the same
temperature variation. 2. Screens for temperature response mutants using reporter genes. We have characterized several transgenic plants with temperature responsive reporter genes likely reflecting different signaling pathways. The first reporter gene is pCOR15a::GUS that is induced by a downshift from 28C to 22C. The second one is pSHP18.2::GUS that is induced by an upshift from 22C to 28C. The third one is pPR1::GUS that is induced by a 22C to 16C shift in a SA-dependent manner. M2 plants from EMS mutagensis are now being screened for mutants with abnormal responses to temperature shifts. To this date, four mutants have been isolated and confirmed and more mutants are expected to come out. Map-based cloning will be carried out to isolate the corresponding genes. 3. Isolation of a temperature sensitive cis-element in a defense related gene. We carried out a detailed study of the promoter of one defense related gene BAP1 to isolate cis-acting elements responsible for temperature
regulation. Analysis of a promoter deletion series of the BAP1 gene revealed a fragment of 40 bp that confers a 28C to 22C induction to a reporter gene. This fragment does not contain any known temperature-responsive elements, and it will be used to isolate genes in transcriptional control by temperature. 4. Screens for mutants defective in temperature modulation of defense responses. bon1-1 and snc1-1 have temperature-dependent dwarf phenotypes due to an inhibition of defense response by a high temperature. We are isolating mutants that are insensitive to high temperature rescue (named 'int') in bon1-1 and snc1-1 backgrounds respectively. To this date, one int mutant from bon1-1 and three from snc1-1 have been confirmed as bon1- or snc1- dependent rather than general dwarf mutant at 28C. We are now in the process of isolating these INT genes through tagging or map-based cloning. The revelation of their molecular identities will generate insights on the interplay between defense and
temperature responses.
Impacts
We have started to characterize and genetically dissect in plants non-extreme temperature responses whose molecular mechanisms are poorly understood. We compared responses to extreme and non-extreme temperatures, and found both shared and distinct mechanisms. This provides us the basis to further study the non-extreme responses. We identified a number of temperature responsive marker genes which have allowed us to carry out genetic screens for mutants in transcriptional regulation by temperature. In addition, we have begun to genetically dissect the modulation of defense responses by temperature in two defense response mutants. A number of mutants have been identified in the genetic screens, and we are now in the process of molecular cloning of these genes. We expect that the revealing of the molecular identities of these genes will shed light on the pathways mediating temperature sensing and signaling and their interaction with other responses (such as defense
responses). This will lay the foundation for improving agriculture and preserving our ecosystem. With this knowledge, we will be able to better understand and predict the impact of local and global climate changes as well as to engineer or select plants with specific growth and defense properties to reduce the adverse impact of temperature on agriculture and ecosystems.
Publications
- No publications reported this period
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