การศึกษาการแสดงออกของยีน NCED ที่เกี่ยวข้องกับการสะสมกรดแอบไซซิกในสภาวะขาดน้ำของต้นกล้ายางพารา

Abstract

Drought condition affects the physiological changes of plant and gene expression patterns. Under drought condition, plants have to adapt for survival such as stomatal closure to reduce dehydration and to maintain water balance in the cell. The hormone that associated with this process is ABA (abscisic acid) which synthesized by 9-cis-epoxycarotenoid dioxygenase (NCED) gene. This research was studied on morphology relative water content, maximum quantum efficiency of photosystem II (F/F), electrolyte leakage and relative chlorophyll content of PB 5/51, RRIM 600, RRIM 623, RRIT 408, RRIT 251 and BPM 24 rubber clones under water deficit condition at 0, 1, 3, 5, 7, 9 and 11 days. Under drought condition dehydrated, relative water content and maximum quantum efficiency of photosystem II (F/F) were continuously decreased while the electrolyte leakage increased and relative chlorophyll content was stable. Based on the physiological responses of rubber clones, they were divided into three groups: drought tolerance group includes RRIM 623 and RRIT 408. The moderate tolerance group includes RRIT 251 and RRIM 600. The susceptible group includes BPM 24 and PB 5/51. Subsequently, RRIM 623, RRIT 408 and PB 5/51 were chosen for investigation of abscisic acid accumulation and gene expression of 9-cis-epoxycarotenoid dioxygenase (NCED) under drought condition. Therefore, NCED3 gene from rubber tree was cloned and analyzed. The cDNA of NCED3 gene contains a complete open reading frame (ORF) of 1,785 bps. The nucleotide sequence showed similarity to the NCED3 gene from Manihot esculenta 91% and Jatropha curcas 83%. For gene expression analysis. RRIT 408 and RRIM 623 exhibited similar expression pattern with stable expression at 0, 1, 3 and 5 days after water withholding and increased to the highest level at 7 days after water withholding. PB 5/51 showed the increased expression of NCED3 gene after 1 day of water withholding and reached maximum level at 5 days after water withholding then decreased especially on 9 days after water withholding. However, NCED3 transcription level of RRIT 408 and PB 5/51 showed higher expression compare to RRIM 623 which is drought tolerant clone and corresponded to the accumulation of abscisic acid. RRIM 623 accumulated abscisic acid less than RRIT 408 and PB 5/51. PB 5/51 rapidly increased in abscisic acid at the early stage of drought condition while RRIT 408 and RRIM 623 gradually increased especially at 7 days after water withholding. In addition, sensitivity of stomata response to abscisic acid showed that RRIM 623 have higher sensitivity than RRIT 408 and PB 5/51. This may result in better drought adaptation of RRIM 623 even though the amount of abscisic acid accumulation was less than that of RRIT 408 and PB 5/51 during drought conditions.