The correlation of the temperature to Nucleo-cytoplasmic distribution of AtHsfA6b and phenotype of Arabidopsis hit2/xpola mutant

• Main Authors: Siao-Ru Jhou, 周筱儒
• Other Authors: Shaw-Jye Wu
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/7qs5z6

碩士 === 國立中央大學 === 生命科學系 === 107 === Arabidopsis heat-intolerant 2（hit2）mutant was isolated because it displays heat and light sensitive phenotypes. The mutated locus was later mapped to be at the EXPORTIN1A（XPO1A）gene, which encodes a nuclear transport receptor whose function is to mediate transportation of nuclear export sequence（NES）-containing proteins from nucleus to cytoplasm. There are two XPO1 homologous genes, HIT2/XPO1A and XPO1B, in Arabidopsis genome, and they share ~87% amino acid sequence identity. However, only hit2/xpo1a but not xpo1b mutant plants exhibit heat- and high light-sensitivities phenotypes. This indicates that HIT2/XPO1Aand XPO1B are not functionally redundant, and implies the existence of HIT2/XPO1A -specific substrate. It is known that many heat stress transcription factors（HSFs）contain both nuclear localization sequence nuclear localization signal（NLS）and nuclear export signal（NES）, and are the major regulators for heat and high light stress responses in plant. To identify which of them might cause hit2/xpo1a phenotypes, we started by examining the intracellular localization of green fluorescent protein（GFP）-tagged HSFs in protoplasts prepared from WT, hit2/xpo1a and xpo1b leaves, at both normal（22°C）and high（37°C）temperature conditions. These results indicated that AtHSFA6b is HIT2/XPO1A-specific substrate. Both AtHsfA6b/a6b-1 and AtHsfA6bΔNES/a6b-1 are not sensitive to high-temperatures. These indicated that the retaintion of AtHsfA6b in the nucleous is not the cause resulting the hit2/xpo1a heat-intolerant phenotypes. I therefore examined the responses of AtHsfA6b/a6b-1 and AtHsfA6bΔNES/a6b-1 to other environmental stimuli and compared to that hit2/xpo1a. Results indicated that the Nucleo-cytoplasmic distribution of AtHsfA6b is necessary for plant to tolerate certain types of eveironmental stresses other than high temperatures. However, we found that hit2 and AtHsfA6bΔNES/a6b-1 has freezing-sensitive phynotype. AtHsfA6b/a6b-1 is not sensitive to freezing. At different degrees, how nucleo-cytiplasmic transport of AtHsfA6b cause the confining AtHsfA6b in nucleus of the different phenotype.