微型核糖核酸2111及169對圓葉菸草(Nicotiana benthamiana)在缺磷和乾旱逆境耐受性上所扮演的角色

Abstract

近年來許多研究指出微型核糖核酸(microRNA, miRNA)，在植物非生物性逆境耐受性中扮演關鍵角色，其中miR2111和miR169受缺磷逆境或乾旱逆境所調控。為了研究圓葉菸草nbe-miR2111及nbe-miR169在缺磷逆境及乾旱逆境所扮演的角色，我們分別產生大量表現nbe-miR2111 (簡稱PCoYMV::nbe-miR2111)和nbe-miR169 (簡稱P35S::nbe-miR169)的轉殖圓葉菸草，並各選取三個株系(Line)與野生菸草在幼苗與成株階段進行缺磷或乾旱處理。結果顯示轉殖株在500 μM (正常磷)、50 μM (低磷)與0 μM (無磷)處理下，PCoYMV::nbe-miR2111與P35S::nbe-miR169轉殖成株與幼苗，多數植株性狀不具一致結果或與WT無顯著差異。無磷處理下，P35S::nbe-miR169轉殖株下位葉先出現壞疽情形，但恢復磷肥供應後，轉殖株地上部鮮重顯著高於WT，暗示轉殖株可能透過犧牲下位葉而在恢復供磷後有較WT佳的復原能力。乾旱逆境並重新復水試驗，P35S::nbe-miR169轉殖株有較好的恢復能力，例如：葉片不再萎凋下垂、較高的地上部鮮重、較高的相對含水量與較高的抗氧化酵素活性，如抗壞血酸過氧化酶(ascorbate peroxidase, APX)與過氧化氫酶(catalase, CAT)活性提高，而相對電解質滲漏率、過氧化氫(hydrogen peroxide, H2O2)濃度、丙二醛(malondialdehyde, MDA)濃度、脯胺酸(proline)與損傷細胞等逆境指標也較低，轉殖株中以Line 12-3表現最佳，Line 3-5次之，Line 1-1僅優於WT。

In recent years, many researches have pointed out that plant microRNAs (miRNAs) play key roles in abiotic stresses tolerance. Among them, miR2111 and miR169 were regulates by the phosphorus deficiency and drought stress in previous studies. To explore the roles of nbe-miR2111 and nbe-miR169 in response to phosphorus deficiency and drought stress in tobacco (Nicotiana benthamiana), we generated transgenic tobacco which overexpress nbe-miR2111 (PCoYMV::nbe-miR2111) and nbe-miR169 (P35S::nbe-miR169). Wild-type (WT) tobacco and three transgenic lines were subjected to phosphorus deficiency and drought treatment at the seedling and adult stage. Most of the measurement items showed no consistent results or no significant difference between PCoYMV::nbe-miR2111 and P35S::nbe-miR169 with WT seedlings and adult plants under three different phosphorus concentrations: 500 μM (normal phosphorus), 50 μM (low phosphorus) and 0 μM (absence of phosphorus). Under the treatment of absence of phosphorus, the lower leaves of P35S::nbe-miR169 transgenic plants first appeared necrosis. However, after re-supply of phosphorus fertilizer, the fresh weight of P35S::nbe-miR169 transgenic plants was significantly higher than that of WT, suggesting that the transgenic plants may have better recovery ability than WT by sacrificing the lower leaves under treatment of absence of phosphorus. After drought stress and re-watering, the P35S::nbe-miR169 transgenic plants have better resilience, such as leaves no longer droop, higher shoot fresh weight, higher relative water content and higher antioxidant enzyme activities- including higher ascorbate peroxidase (APX) and catalase (CAT) activity. Stress indicators, such relativity electrolyte leakage, hydrogen peroxide (H2O2) concentration, malondialdehyde (MDA) concentrations, proline content and damaged cells was lower than WT. Within transgenic plants, line 12-3 is the best and then is line 3-5, line 1-1 only better than WT.