การตอบสนองทางสรีรวิทยาและการแสดงออกของยีน P5CS ที่เกี่ยวข้องกับการสะสบโพรลีนในสภาวะขาดน้ำของต้นกล้ายางพารา

Abstract

In rubber plantation, seedling stage requires sufficient water for growth. Lack of water can cause serious damage. Therefore, using drought tolerant varieties can minimize the loss of rubber seedlings. Insufficient water intake will result in disruption of growth as well as physiological and chemical changes. In this study, changes in relative water content in the leaves, electrolyte leakage, maximum quantum efficiency of photosystem II (F/F) and relative chlorophyll content of PB 5/51, RRIT 408, RRIM 623, RRIM 600, BPM 24 and RRIT 251 were studied at different time points of water deficit conditions (0, 1, 3, 5, 7, 9 and 11 days after water withholding). During water deficit, relative water content, maximum quantum efficiency of photosystem II (F/Fm) and relative chlorophyll content were decreased. On the contrary, the electrolyte leakage was increased. Genotypic variation was observed among different rubber clones. Based on those results, rubber clones were divided into two groups: drought tolerance group includes RRIM 623, RRIT 408, RRIM 600 and RRIT 251 and susceptible group includes PB 5/51 and BPM 24. Subsequently, RRIM 623, RRIT 408 and PB 5/51 were chosen as representative of drought tolerant (RRIM 623 and RRIT 408) and drought sensitive (PB 5/51) clones for investigation of proline accumulation and expression of pyrroline-5-carboxylate synthetase (P5CS) gene. PB 5/51 expressed the highest amount of P5CS gene at 5 days after water withholding but the expression was reduced quickly afterward. On the contrary, proline accumulation of PB 5/51 was gradually increased starting from 7 days after water withholding. Whereas enhanced expression of P5CS in RRIM 623 and RRIT 408 was detected at 7 days after water withholding and reached maximum level at 9 days after water withholding. Proline accumulation, however, continued to increase. Therefore, no correlation between P5CS expression and proline accumulation in rubber seedling under drought was observed. This might due to different strategies of proline accumulation were implemented in different rubber genotypes. Other key enzymes might involve in this phenomena such as P5CR. However, drought sensitive (PB 5/51) and drought tolerant (RRIM 623 and RRIT 408) showed different P5CS expression patterns.