植物生态学报 ›› 2020, Vol. 44 ›› Issue (6): 677-686.DOI: 10.17521/cjpe.2020.0058

所属专题: 光合作用 根系生态学

• 研究论文 • 上一篇    下一篇

干旱胁迫对转PtPIP2;8基因84K杨苗木光合、生长和根系结构的影响

刘丽燕1,2, 冯锦霞1, 刘文鑫3, 万贤崇1,*()   

  1. 1中国林业科学研究院林业新技术研究所, 北京 100091
    2新疆林业科学院造林治沙研究所, 乌鲁木齐 830063
    3九江学院药学与生命科学学院, 江西九江 332000
  • 收稿日期:2020-03-06 接受日期:2020-04-23 出版日期:2020-06-20 发布日期:2020-06-12
  • 通讯作者: 万贤崇
  • 基金资助:
    国家自然科学基金中央级公益性科研院所基本科研业务费专项资金(31270648)

Effects of drought stress on photosynthesis, growth and root structure of transgenic PtPIP2;8 poplar 84K (Populus alba × P. glandulosa)

LIU Li-Yan1,2, FENG Jin-Xia1, LIU Wen-Xin3, WAN Xian-Chong1,*()   

  1. 1Research Institute of Forestry New Technology, Chinese Academy of Forestry, Beijing 100091, China
    2Afforestation and Sand Control Institute of Xinjiang Academy of Forestry, ürümqi 830063, China
    3School of Pharmacy and Life Sciences, Jiujiang University, Jiujiang, Jiangxi 332000, China
  • Received:2020-03-06 Accepted:2020-04-23 Online:2020-06-20 Published:2020-06-12
  • Contact: WAN Xian-Chong
  • Supported by:
    National Natural Science Foundation of China(31270648)

摘要:

为研究水通道蛋白PtPIP2;8基因功能, 了解其不同表达水平的转基因84K杨(Populus alba × P. glandulossa)应对干旱胁迫的响应, 该文以转PtPIP2;8 84K杨抑制表达株系(抑制表达)、野生型(WT)和转PtPIP2;8 84K杨超表达株系(超表达)为试验材料, 测定PtPIP2;8表达水平、根系导度、光响应曲线、气体交换参数、生长及根系形态指标。结果显示: (1) WT植株PtPIP2;8仅在根系表达; 超表达植株PtPIP2;8除在根部显著表达外, 在茎和叶片中也显著表达; 抑制表达植株PtPIP2;8仅在根部有微量表达, 表达量分别是WT和超表达植株的1/20和1/80。(2)根系结构分析发现, 超表达植株总根长、总根表面积、总根体积、总根尖数显著低于WT和抑制表达植株, 根系导水率显著高于WT和抑制表达植株, 表明PtPIP2;8参与了植物根系水分运输, 提高了水分运输效率。(3)正常水分条件下, 抑制表达植株苗高、叶面积显著低于WT和超表达植株, 根冠比显著高于WT和超表达植株。干旱胁迫后, 抑制表达植株净光合速率(Pn)、气孔导度(Gs)下降幅度小, 仍能维持较高的Pn。气体交换参数显示抑制表达植株PnGs日变化为“单峰”型, 属气孔因素引起的净光合速率下降;WT和超表达植株PnGs日变化为“双峰”型, 干旱胁迫后, 抑制表达植株Pn略微下降, WT和超表达植株Pn均下降, 尤其是13:00、15:00下降显著, 表明WT和超表达植株对干旱胁迫更加敏感, 干旱对其影响更大。(4)干旱胁迫后, 抑制表达植株相对生长速率、总生物量降低的最少, 根冠比最高; 总根表面积、总根体积、总根尖数显著高于WT植株。表明PtPIP2;8直接参与水分运输并提高水分运输效率, 其转化影响了植株根系发育和生长。超表达植株根系发育的下降和叶面积的增大减弱了它的抗旱性, 而抑制表达植株矮小, 降低的叶面积, 增加的根系生长和根冠比提高了它的抗旱能力。从研究结果来看, 水通道蛋白提高了水分跨膜运输效率, 而非水通道蛋白导水机制对干旱有较强的耐受性。

关键词: 干旱胁迫, 转基因杨树, 光合特性, 根系结构

Abstract:

Aims In this study, changes in growth, photosynthesis and root structure in response to drought were tested in transgenic poplar 84K (Populus alba × P. glandulosa) seedlings with different expression levels of aquaporin gene (PtPIP2;8). The function of aquaporin gene PtPIP2;8 and its response to drought stress were analyzed.
Methods We selected PtPIP2;8 silencing line of poplar 84K, PtPIP2;8 overexpressing line of poplar 84K and wildtype (WT) as the experimental materials. The Real-time fluorescence quantitative PCR technique was used to detect the PtPIP2;8 expression in roots, stems and leaves. Root hydraulic conductance was measured by high pressure liquid flow meter. The photosynthetic light-response curve, and gas exchange parameters were measured by a LI-6400 photosynthetic system. Growth indexes were determined, and the root length, root surface area, root volume and total root tips were scanned and then analyzed with the root analysis software.
Important findings The results showed that: (1) The gene PtPIP2;8 was mainly expressed in the root system in WT, while its significant expression occurs not only in roots, but also in stems and leaves in PtPIP2;8 overexpressing poplar lines. The PtPIP2;8 RNAi-silence poplar lines only showed weak expression of PtPIP2;8 in the root, and the expression level were 1/20 and 1/80 of WT and overexpression line, respectively. (2) The root structure analysis showed that overexpression lines had significantly lower total root length, total root surface area, total root volume and total root tips than RNAi-silence line and WT, but higher root hydraulic conductance compared with RNAi-silence line and WT. These results showed that the aquaporin gene PtPIP2;8 participated in plant water transport and improved water transport efficiency. (3) Under normal water conditions, RNAi-silence lines showed lower plant height and leaf area but higher root-shoot ratio compared with overexpression line and WT. After drought stress, RNAi-silence lines only slightly decreased the net photosynthetic rate (Pn) and stomatal conductance (Gs), and maintained a relatively high Pn. Diurnal changes of Pn and Gs in RNAi-silence lines showed a single-peak pattern, in which the decrease of photosynthesis was caused by stomatal limitation. Diurnal changes of Pn in both overexpression lines and WT had a two-peak pattern, indicating the non-stomatal limitation of photosynthesis. Drought stress slightly decreased Pn of RNAi-silence lines, while largely decreased Pn of overexpression line and WT decreased, especially at 13:00 and 15:00, indicating that overexpression line and WT were more sensitive to drought stress compared with the RNAi-silence lines. (4) Under drought stress, RNAi-silence line showed the least decline in relative growth rate and total biomass, and the highest root-shoot ratio among the three poplar lines. The total root surface area, total root volume and total root tips of RNAi-silence line were significantly higher than those of WT. The results suggest that aquaporin gene PtPIP2;8 directly participates in the water transport and helps to improve the water transport efficiency, thus the transformation of aquaporin PtPIP2;8 gene may affect root development and growth of plants. Overexpression lines weaken their drought resistance with decreased root development and increased leaf area, while RNAi-silence line increases its drought resistance with reduced leaf area, increased root growth and root-shoot ratio. The results of this study indicate that aquaporin improves the efficiency of water transport across membranes, while the non-aquaporin water-conducting mechanism has greater tolerance to drought.

Key words: drought stress, transgenic poplar, photosynthetic characteristics, root structure