燕麦光合、碳代谢对碱胁迫的响应机制及外源精胺缓解效应研究

Soil salinization and alkalization are two primary limiting factors to agricultural production. In Inner Mongolia, 23.8% of the available arable land is alkalinized and salinized. Previous studies have mostly concentrated on salt stress while alkali stress has received little attention. In fact, the significant extent of damage to production due to alkali stress is more serious than salt stress. It is urgent to improve the alkaline land. Our previous study indicated that alkali stress could cause the appearance of yellow leave. We hypothesize that the disruption of chlorophyll metabolism led by alkali stress could inhibit the photosynthesis, and then decrease the production. It has been reported that spermine could improve the resistance for crop to many abiotic stresses. Oat is considered as an important crop in Inner Mongolia and will be used in this study. In order to find the reason for the decrease of chlorophyll contents under alkali stress, we plan to study the expression of key enzyme and intermediate in the synthesis and degradation of chlorophyll. Effects of exogenous spermine on the CO2 assimilation efficiency, PSII primary photochemical reaction, carbohydrate metabolism and distribution under alkali stress will be studied. We want to demonstrate the key physiological mechanism of yield reduction under alkali stress, and the effects of exogenous spermine on yield in alkalinity. In addition, we plan to use the proteomic method to find the differential expression proteins and biological paths led by exogenous spermine under alkali stress. The results may provide the theory basis for the oat cultivation and breeding in saline-alkaline land.

内蒙古盐碱土面积较大，占耕地面积的23.8%，是制约农作物增产的重要原因。与盐胁迫相比，碱胁迫对产量抑制作用更强，然而碱胁迫相关研究仍然较为局限，如何提高作物抗碱性是亟待解决的难题。作物产量的90-95%来源于光合作用，申请者前期试验发现碱处理导致叶片大面积黄化，据此可以推测，碱胁迫下，叶绿素代谢受阻进而抑制光合作用是作物减产的关键点。精胺在多种非生物胁迫下可明显改良作物抗性。鉴于此，本项目以内蒙古优势特色作物燕麦为研究对象，围绕光合特性，通过分析叶绿素合成降解过程，识别碱胁迫下，叶绿素积累的受阻位点。从CO2同化、PSII原初光化学反应以及光合产物代谢分配等方面，明确碱胁迫抑制产量生成的关键生理步骤以及碱胁迫下外源精胺对产量生成的调控机制。进一步运用蛋白组方法，找到碱、碱+精胺处理间差异表达蛋白，明确精胺调控燕麦抗碱性信号通路，以为盐碱化土地燕麦栽培及抗性品种选育提供理论依据。

土壤碱化是抑制作物产量生成的重要原因，而其减产机制尚未探明。本研究以燕麦为研究对象，立足光合，运用电镜、RNA-seq,DIA蛋白组检测技术开展了碱胁迫及外施精胺对燕麦光合、碳水化合物影响效应相关试验。主要研究结果表明：1）碱胁迫，下调HEMA、ALAD等基因，降低δ氨基酮戊酸等叶绿素中间代谢物含量，抑制叶绿素合成，同时升高pheophorbide a oxygenase蛋白表达量，加速叶绿素分解，导致碱处理下，叶绿素含量显著降低，进而抑制光合速率及碳水化合物生产。外源精胺可上调部分叶绿素合成基因，降低叶绿素分解蛋白pheophorbide a oxygenase表达量，较单碱胁迫升高叶绿素积累量。2）碱胁迫下，叶绿素荧光参数Fo升高，Fv/Fm、ABS/CSm、TrO/CSm、EtO/CSm降低，说明PSⅡ反应中心破坏。碱胁迫导致表观量子效率、羧化效率降低，其中抽穗、灌浆期减幅高于拔节期。外施精胺缓解碱胁迫对PSⅡ抑制作用，升高光能利用率。3）碱胁迫下，叶片、根可溶性糖、蔗糖、葡萄糖、果糖含量升高以进行渗透调节，外施精胺较单碱胁迫降低叶片可溶性糖含量，以利于生长发育。4）碱及外施精胺处理下，在拔节、抽穗、灌浆期，鉴定出生长发育、抗氧化、光合、水分吸收、碳水化合物相关差异表达蛋白及抗性品种间差异蛋白，从蛋白水平揭示碱胁迫减产机制及外施精胺缓解效应。