Frontiers | Modulating Drought Stress Response of Maize by a Synthetic Bacterial Community (frontiersin.org)

摘要

众所周知，植物对环境胁迫的感知和反应包含一套复杂的机制，微生物组参与其中。因此，了解植物生理反应对于理解微生物组对植物恢复力的贡献至关重要。然而，由于植物生长是一个动态过程，一个主要障碍是找到合适的工具来有效地测量不同植物生理参数的时间变化。在这里，我们在一对一（植物传感器）的设置中使用了一个非侵入性实时表型平台，以研究含有植物有益细菌的合成群落（SynCom）对三个商业玉米杂交种对干旱胁迫（DS）的生理学和反应的影响。SynCom接种显著减少了产量损失并调节了重要的生理特性。SynCom接种的植物显示出较低的叶温度，在严重DS下减少了膨压损失，并且在补水后恢复更快，这可能是由于液流调节和更好的水利用。微生物组分析显示，SynCom细菌成员能够在成熟的植物上牢固地定植，并招募土壤/种子传播的有益微生物。高分辨率的时间数据使我们能够记录植物对日常环境波动的即时反应，从而揭示微生物组在调节玉米生理、抗旱能力和作物生产力方面的影响。

FIGURE 1. A SynCom containing beneficial microbes induces a physiological response against DS in three commercial maize hybrids. (A) Plants kept in SDS for 29 days (79 DAS) had their leaves rolled inward, and older leaves fell for all hybrids, regardless of whether they were inoculated. (B) P3707VYH was the less tolerant hybrid in the absence of SynCom, completely bent after 31 days of SDS (81 DAS), in contrast to the inoculated hybrid (white arrow). (C) Uninoculated DKB177 and SX7341 were completely bent (83 DAS), as shown by the white arrows. In the presence of SynCom, plants were maintained in a straight position (DKB177) and partially or completely bent (SX7341 and P3707VYH, respectively), as shown by the black arrows. (D) Inoculated plants (SX7341 and particularly P3707VYH) straightened 2 days after rewatering (86 DAS; black arrows), while uninoculated plants were not capable of completely recovering their structure (white arrows). Detailed results are shown in Supplementary Figure 3 and Supplementary Movie 1. WW, well watering; DS, drought stress; DAS, days after sowing; SDS, severe drought stress.

图1 含有有益微生物的SynCom在三个商业玉米杂交种中诱导了针对干旱胁迫的生理反应。（A） 在严重干旱胁迫中保持29天（播种后79天）的植物，其叶片向内卷曲，所有杂交种的老叶掉落，无论是否接种。（B）在严重干旱胁迫中保持31天（播种后81天）后，与接种SynCom的杂交种（白色箭头）相比，未接种的P3707VYH杂交种耐受性较差。（C） 未接种的DKB177和SX7341完全弯曲（播种后83天），如白色箭头所示。在SynCom的存在下，如黑色箭头所示，植物保持在笔直位（DKB177）和部分或完全弯曲（分别为SX7341和P3707VYH）。（D） 接种的植物（SX7341，特别是P3707VYH）在重新浇水后2天变直（播种后86天；黑色箭头），而未接种的植物不能完全恢复其结构（白色箭头）。

FIGURE 2. Synthetic community (SynCom) inoculation reduces the yield loss of commercial maize hybrids under DS. During DS, inoculated DKB177 and P3707VYH plants displayed higher (A) yield per plant (3.93× and 3.45×, respectively), (B) number of kernels per plant (3.87× and 3.85×, in that same order) and (C) number of kernel rows per ear (42 and 59%, respectively) under DS. Additional yield results are shown in Supplementary Figure 5. Values expressed as the mean ± SD. n ≥ 7 plants per treatment. WW, well watering; DS, drought stress; SD, standard deviation. **P ≤ 0.01 and ***P ≤ 0.001.

图2 合成群落（SynCom）接种减少了商品玉米杂交种在干旱胁迫下的产量损失。在干旱胁迫期间，接种的DKB177和P3707VYH植株表现出较高的（A）单株产量（分别为3.93×和3.45×），（B）单株籽粒数（3.87×和3.85×，顺序相同）和（C）每穗籽粒行数（分别为42%和59%）。附加产量结果如补充图5所示。数值表示为平均值±SD.n≥7株/处理。WW，井水；DS，干旱胁迫；SD，标准偏差**P≤0.01，***P≤0.001。

FIGURE 3. Fluctuation of environmental parameters detected by the non-invasive real-time phenotyping platform. (A) Air temperature, with minimum and maximum observed at 11 DAS at 5:30 am (11.35 ± 0.05°C) and 107 DAS at 2:00 pm (51.38 ± 1.93°C), respectively (black arrows). (B) RH, with a minimum of 18.85 ± 0.15% at 8 DAS at 4:30 pm (black arrow). (C) VPD, found to reach a peak of 7.17 ± 0.60 kPa at 107 DAS at 2:15 pm (black arrow), following the high air temperature variation at that moment. (D) PAR, with a maximum peak of 400.53 ± 1.94 μmol m–2 s–1 observed at 53 DAS at 12:00 pm (black arrow). Gray background highlights period of DS treatment. Data points were missing from 12 to 25 DAS due to an unexpected disruption of the automated measuring routine. DAS, days after sowing; RH, air relative humidity; VPD, vapor-pressure deficit; PAR, photosynthetically active radiation; DS, drought stress.

图3 无创实时表型平台检测到的环境参数波动。（A） 空气温度，分别在播种后11天上午5:30（11.35±0.05°C）和播种后107天下午2:00（51.38±1.93°C）观察到最低和最高温度（黑色箭头）。（B） 相对湿度，播种后8天下午4:30（黑色箭头）时最小值为18.85±0.15%。（C） 蒸汽压不足，在播种后107天下午2时15分达到7.17±0.60 kPa的峰值（黑色箭头），随着当时的高空气温度变化。（D） 光合作用有效辐射，最大峰值400.53±1.94μmol m–2 s–1，于播种后53天下午12:00观察到（黑色箭头）。灰色背景突出显示干旱胁迫处理的周期。由于自动测量程序意外中断，播种后12至25天的数据点缺失。

FIGURE 4. The SynCom-inoculated DKB177 plants displayed lower Tleaf than uninoculated plants. (A) The hybrid DKB177 showed a low Tleaf when inoculated with SynCom, especially in periods when the air temperature was high. The standard deviation is shown as the background for air temperature and both treatments. (B) Tleaf of uninoculated plants reaches a peak of 3.23°C higher at 106 DAS (inset from panel A). (C) The difference between Tleaf of inoculated and uninoculated plants (ΔTleaf), rounded every 30 min over time, revealed consistency in the high temperature presented by uninoculated DKB177. Values were displayed above the x-axis when Tleaf of inoculated plants is higher than Tleaf of uninoculated plants or below the x-axis when Tleaf of uninoculated plants is higher than Tleaf of inoculated plants, and colored in blue or red, respectively, when significantly different (P ≤ 0.05). Areas filled with light gray denote not statistically significant differences. The sums of areas in the graph above and below the x-axis were considered only for statistically significant differences. See Supplementary Figure 8 for the entire analyzed period. Tleaf, leaf temperature; ΔTleaf, difference of Tleaf; aau, arbitrary area units; DAS, days after sowing.

图4。SynCom接种的DKB177植物的Tleaf低于未接种的植物。（A） 当接种SynCom时，杂交种DKB177表现出低Tleaf，特别是在空气温度较高的时期。标准偏差显示为空气温度和两种处理的背景。（B） 未接种植物的叶片在106 DAS时达到3.23°C的峰值（插图来自图a）。（C） 接种和未接种植物的Tleaf之间的差异（ΔTleaf）随时间每30分钟舍入一次，显示了未接种DKB177所呈现的高温的一致性。当接种植物的Tleaf高于未接种植物的T leaf时，值显示在x轴上方，当未接种植物Tleaf低于接种植物的t leaf时显示在x轴向下方，当显著差异时，值分别显示为蓝色或红色（P≤0.05）。浅灰色填充的区域表示无统计学显著差异。图中x轴上方和下方的面积总和仅用于统计显著差异。整个分析期见补充图8。Tleaf，叶温；ΔTleaf，Tleaf的差值；aau，任意面积单位；DAS，播种后几天。

FIGURE 5. Synthetic community (SynCom) inoculation affects the sap flow of maize hybrids. (A) Fluctuation of VPD (kPa) from 77 to 83 DAS. The gray background highlights daily windows from 10:00 am to 4:00 pm, periods considered to measure sap flow of DKB177 (B,C), SX7341 (D,E), and P3707VYH (F,G). Box plots are shown for WW- (B,D,F) and DS-treated/rehydrated (C,E,G) plants. Rehydration was performed at 80 DAS. (B) In WW, SynCom leads to an increase in DKB177 sap flow by up to 2.22×. (C) Inoculated DKB177 plants tended to have their sap flow reduced in late stages of DS (77–79 DAS). During recovery (81–83 DAS), this reduction significantly reached up to 25.9%. (D) SX7341 presented an undefined pattern of sap flow under WW the regime. (E) A lack of pattern was also found during the DS and rehydration periods. (F) WW-treated P3707VYH had its sap flow reduced by up to 39.7% when inoculated, the same effect found in DS (G). (G) During recovery, SynCom inoculation led to a shift in sap flow of P3707VYH with an increase of up to 2.57× compared to the control. VPD: vapor-pressure deficit; WW, well watering; DS, drought stress; DAS, days after sowing. *P ≤ 0.05, **P ≤ 0.01, and ***P ≤ 0.001.

图5。合成群落（SynCom）接种影响玉米杂交种的液流。（A） VPD（kPa）从77到83 DAS的波动。灰色背景突出显示每天上午10:00至下午4:00的时段，这些时段被视为测量DKB177（B，C）、SX7341（D，E）和P3707VYH（F，G）的树液流量。显示了WW-（B、D、F）和DS处理/再水合（C、E、G）植物的方框图。在80DAS时进行补水。（B） 在WW中，SynCom导致DKB177的液流增加了2.22倍。（C）接种DKB177植物在DS后期（77-79 DAS）的液流趋于减少。在恢复期间（81–83 DAS），这种减少显著达到25.9%。（D）SX7341在WW状态下呈现出未定义的液流模式。（E） 在DS和补液期间也发现缺乏模式。（F） WW处理的P3707VYH在接种时其液流减少了39.7%，与DS（G）中发现的效果相同。（G） 在恢复期间，SynCom接种导致P3707VYH的液流发生变化，与对照相比增加了2.57倍。VPD：蒸汽压不足；WW，井水；DS，干旱胁迫；DAS，播种后几天*P≤0.05，**P≤0.01，***P≤0.001。

FIGURE 6. Members of SynCom robustly colonize different maize hybrids. (A) PCoA of the Bray–Curtis dissimilarity matrix of inoculated and uninoculated plants. (B) Relative abundance of OTUs present in SynCom in WW- and DS-treated inoculated and uninoculated DKB177, SX7341, and P3707VYH hybrids. (C) Relative abundance of community-based isolates in SynCom in WW- and DS-treated inoculated and uninoculated maize hybrids. OTUs of community-based isolates identified as robust colonizers are individually highlighted in Supplementary Table 3. Values expressed as the mean ± SD. PCoA, principal coordinates analysis; SD, standard deviation; Un., unknown. *P ≤ 0.05, **P ≤ 0.01, and ***P ≤ 0.001.

图6。SynCom的成员在不同的玉米杂交种上进行了强有力的定殖。（A） 接种和未接种植物的Bray–Curtis相异矩阵的PCoA。（B） WW和DS处理的接种和未接种DKB177、SX7341和P3707VYH杂交种中SynCom中存在的OTU的相对丰度。（C） WW和DS处理的接种和未接种玉米杂交种中SynCom社区分离物的相对丰度。补充表3中单独强调了被鉴定为强大殖民者的社区隔离物的OTU。值表示为平均值±SD.PCoA，主坐标分析；SD，标准偏差；联合国。，未知*P≤0.05，**P≤0.01，***P≤0.001。