Isolation, Identification And Functional Analysis Of The Proteins Related To The Phenotypes Of Arabidopsis Mutants Lpt1 And Lks1

The proteins related to the phenotypes of Arabidopsis low-phosphorus-tolerant mutant lpt1-1 and low-K+-sensitive mutant lks1-1were identified and their possible roles in plant responses to the nutrient-deficient stresses were analyzed.lptl-1 mutants could grow continually and their shoots didn t show typical Pi-deficient symptom (purple-colored shoots) under low-phosphorous stress. After the seedlings of both wild-type and lptl-1 mutant were treated in the low-Pi medium for 0, 1, 2 and 4 days, respectively, total proteins were isolated from shoots or roots by using the improved protein preparation protocols and analyzed by conducting IPG-DALT 2D polyacrylamide gel electrophoresis. The results showed that there were 16 differentially expressed proteins identified. Four of them were further analyzed by using MALDI-TOF mass spectrometer, and two of them were identified as cytosolic triosephosphatisomerases and the other two were putative cytosolic glyceraldehyde-3-phosphate dehydrogenase (GapC-2) and putative photosystem I subunit PSI-E protein, respectively.Northern blot analysis demonstrated that the transcription of GapC-2 gene was significantly enhanced by the low-Pi treatment. Two independent T-DNA insertion lines of GapC-2 gene showed more sensitive phenotype than wild-type plants under the low-Pi stress, while the transgenic complementation lines of mutants showed similar phenotype compared to wild-type plants. These results indicate that GapC-2 may somehow participate plant responses to low-Pi stress, probably by involving Pi compartmentation and utilization.The typical phenotypes of the lks1-1 mutants include inhibited overall growth and stopped cotyledons of young seedlings under the low-K+ treatment. After the seedlings of both wild-type and lksl-1 mutant were treated in the low- K+ medium for 12 and 48 hours, respectively, total proteins were prepared from shoots and roots separately. The proteins were analyzed by conducting IPG-DALT 2D polyacrylamide gel electrophoresis and 6 differentially expressed proteins were identified. Three of them were further analyzed by using MALDI-TOF mass spectrometer, including glutathione S-transferase 6 (upregulated in wild-type plants under low-K+ stress), manganese superoxide dismutase and NADP adrenodoxin-like ferredoxin reductase (both upregulated in lks1-1 mutants under low-K+ stress). The further investigations are required to demonstrate their roles in plant responses to low-K+ stress.