荒漠植物内生细菌对拟南芥盐、旱耐受的调控研究

Salt and drought tolerance of plants for desert was correlated with endophytic bacteria tightly. However, the effects were still unknown. Our previous study has proved that the endophytic bacteria from desert plants were salt and alkali resistant and enhance salt and drought tolerance of their host plants. For example, the endophytic bacteria isolated from Ammodendron bifolium, an endangered species of the national grade II, increased its rate of seed germination 10 times under drought stress; the endophytic bacteria isolated from Lepidium perfoliatum, a kind of desert ephemeral plant, produced lots of exopolysaccharides; the endophytic bacteria isolated from the seeds of Caragana leucophloea was salt and alkali tolerant. In order to understanding the effects of salt and drought tolerance of endophytic bacteria from desert plants, Arabidopsis will be inoculated with about 200 endophytic bacteria we've already isolated from desert plants to screen bacterial strain which can enhance Arabidopsis salt and drought tolerance. After that the physiological response and salt and drought stress-resistance indicators, such as proline, nitrate reductase, solubility sugar, abscisic acid, betaine, malondialdehyde will be estimated under NaCl or PEG stresses on seedling development, plant growth with or without inoculation. The results will be helpful for our understanding of the physiological responses of Arabidopsis with or without inoculation with the isolates. And the adaptation mechanism of the plant stress-resistance for desert would be explored. And this will also lay a foundation for the application of endangered desert plants protection and desert ecosystems restoration.

荒漠植物对盐旱的耐受能力与其内生菌密切相关，但其作用途径及调控方式尚未了解。前期研究证实分离自荒漠植物的内生细菌具有耐受高盐碱并提高宿主植物干旱耐受力的特性，其中分离自荒漠濒危植物银沙槐的内生细菌可在高度干旱胁迫下提高种子萌发率10倍以上；分离自荒漠短命植物抱茎独行菜的内生细菌可产生大量胞外多糖；分离自白皮锦鸡儿种子种皮与种仁间的内生细菌存在差异且耐受高盐碱。为了解荒漠植物内生细菌共生盐旱耐受调控作用，本项目以已获得的200多株内生细菌为材料，以模式植物拟南芥为平台，以盐、旱胁迫为逆境条件，试验拟南芥在胁迫下对接种内生细菌的生理响应，检验对幼苗发育和植株生长的影响及各阶段的生理变化，研究源自荒漠植物的内生细菌对拟南芥盐旱耐受的作用途径，探索共生抗逆调控方式，为内生细菌应用于荒漠濒危物种保护和生态恢复奠定理论基础。

荒漠植物内生细菌有助于提高宿主植物抗盐旱等逆境胁迫。为了解荒漠植物内生细菌的作用途径及调控方式，本研究对盐旱胁迫下促拟南芥种子萌发的抱茎独行菜内生细菌的筛选、有效菌株NG4-4共生抗干旱作用方式及其对拟南芥产量和抗逆生理指标等进行了研究。结果表明，有5株内生细菌（NG3-2、NG3-9、NG4-1、NG4-3、NG4-4）在100mM NaCl模拟的盐胁迫下能提高拟南芥种子萌发。分别有1株（NG4-5）、4株（NG4-1、NG4-2、NG4-4、NG4-11）、1株（NG4-6）株和3株（NG3-6、NG3-10、NG4-6）内生细菌在10%、15%、20%和25% PEG 6000模拟的不同干旱胁迫条件下能提高拟南芥种子萌发。内生细菌NG4-4的胞外分泌物及菌液在干旱胁迫下对提高种子萌发率均有作用。在非胁迫条件下和干旱胁迫下，接种内生细菌NG4-4均能使拟南芥提前进行生殖发育，提高拟南芥产量，但是并不影响子代拟南芥种子的萌发率。相关抗逆生理指标的检测结果显示在干旱胁迫下，接种内生细菌NG4-4能通过降低拟南芥幼苗的丙二醛（MDA）含量；提高超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）活性；增加脯氨酸含量等提高拟南芥抗干旱胁迫。实验阶段性成果对揭示荒漠植物共生抗逆调控机制和进一步研究内生细菌应用于荒漠濒危物种保护和生态恢复提供了基础。