Preliminary Functional Analysis Of Gossypium Hirsutum Transcription Factor GhPLATZ

Plants are exposed to various abiotic stresses, such as salinity and drought. The abiotic stresses will directly affect the the crop yield and also can affect the sustainability of ecological environment. Using molecular technology to increase the salt and drought tolerance is the most effective way to keep normal growth and development, and even to raise the productivity.Seed germination is an important stage of plant growth and development. The high concentration of salt can inhibit seed germination. However, the detailed mechanism of salinity on seed germination is still very limited.As one of the important economic crops, cotton has lots of problems when encountered with abiotic stresses, for example, salt. Therefore, studying its responsive mechanism to abiotic stresses will provide a clue to improve the resistance of cotton to abiotic stresses.Through Solexa sequence analysis, we found that one TAG matched to TA23823₃635was upregulated by salt stress and then selected for further study. The results are as follows:（1） Using RACE technology, we obtained the full-length sequence of TA23823₃635. The BLAST analysis indicated that it encoded a protein that belonged to the PLATZ family. To date, it is the only PLATZ in cotton, which is named as GhPLATZ. The phylogenetic tree for domain and amino acid sequence alignments showed that GhPLATZ showed the highest homologies with AtPLATZ3and AtPLATZ11.（2） Expression pattern was detected by qRT-PCR. The results showed that GhPLATZ was ubiquitously expressed in leaves, roots and stems of cotton, with higher expression level in leaves.（3） Also by qRT-PCR, we detected the expressions of GhPLATZ in30-day-old cotton seedlings treated with200mM NaCl,100μM GA,100μM ABA and4℃for6h and12h respectively. The results showed that GhPLATZ could be significantly induced by salt and cold, but not GA and ABA. These data indicated that GhPLATZ might play an important role in response to salt and low temperature.（4） When GhPLATZ transgenic Arabidopsis and WT （wild type） seeds were put on plates containing150mM,175mM,200mM and250mM NaCl respectively. The germination rate and greening rate of transgenic Arabidopsis and WT showed increased inhibition with the NaCl concentraion’s increased. However the germination rate and greening rate of transgenic Arabidopsis always showed higer levels than those of WT, suggesting that GhPLATZ overexpression could lead to the salt insensitivity during germination and postgermination.（5） When GhPLATZ transgenic Arabidopsis and WT seeds were put on plates containing300mM and500mM Man （mannitol） respectively. The germination rate was not significantly different between transgenic Arabidopsis and WT, but the greening rate of the former was obviously higher than the latter, suggesting that GhPLATZ overexpression could lead to the osmotic insensitivity during germination and postgermination.（6） When GhPLATZ transgenic Arabidopsis and WT seeds were put on plates containing3μM and5μM ABA respectively. The WT was a little more sensitive to ABA than transgenic Arabidopsis but not so significant compared to those under NaCl or mannitol condition, suggesting that GhPLATZ might partially depend on ABA to participate in salt and osmotic stess response.（7） The expression levels of ABA biosynthesis related genes, such as ABA1, ABA2, ABA3, AAO3, NCED3, and ABA signaling related genes, such as ABI1, ABI2, ABI3, ABI4, ABI5, were tested under salt condition. The results showed that ABA biosynthesis related genes, such as ABA1, ABA2, ABA3, AAO3, NCED3, showed almost no difference between GhPLATZ overexpressor and WT. ABA signaling related genes, such as ABI1, ABI2, showed similar pattern. However, ABI3, ABI4, ABI5showed much lower expression in GhPLATZ overexpressor than WT. These data indicated that the salt and osmotic insensitivity of GhPLATZ overexpressor might depend on ABI3, ABI4, ABI5signaling during germination and postgermination.