金丝楸幼苗响应盐碱胁迫的生理和转录组分析

目的 研究不同盐碱胁迫对金丝楸幼苗生长、光合和生理指标的影响,并结合转录组测序分析,探究楸树耐盐碱的生理机制和分子机制。 方法 采用盆栽法对金丝楸幼苗进行不同盐碱胁迫处理,分析其生物量、光合及生理指标对不同盐碱响应的差异,采用Illumina高通量测序技术进行转录组测序,通过生物信息学分析盐碱胁迫对转录水平的影响。 结果 不同盐碱胁迫下,金丝楸幼苗叶片受伤害程度为Na2CO3>混合盐碱>NaCl;新增株高和地径、地上部和根的干质量和鲜质量、生物量、根冠比均受到明显抑制,并随盐碱浓度增加而抑制加强,但生长胁迫指数均随浓度的增加而降低;丙二醛（MDA）含量和相对电导率都随胁迫浓度增加而不同程度上升,超氧化物歧化酶（SOD）活性、可溶性糖含量、脯氨酸（Pro）含量、叶绿素总量和光合速率都呈现先上升后下降的趋势。转录组测序共产生约60.4 Gb原始数据,组装得到55 793个Unigenes,其中29 534（52.93%）个Unigenes获得了注释;通过差异表达基因（DEGs）分析,3个比较组（CK vs NaCl,CK vs Na2CO3 和 CK vs 混合盐碱）分别筛选出1 779、2 835和4 059 个DEGs;DEGs GO富集分析表明,膜的整体成分、膜的内在成分、催化活性、类异戊二烯代谢和合成过程、氧化还原酶活性等条目被显著富集;DEGs KEGG分析表明,苯丙素生物合成、淀粉和蔗糖代谢、植物激素信号转导、萜类主干生物合成和精氨酸代谢等通路被显著富集;此外,在DEGs中鉴定的bHLH、ERF、MYB-related、NAC、C2H2、WRKY、MYB和bZIP转录因子家族成员最多。 结论 金丝楸主要通过积累可溶性糖和Pro,提高SOD酶活和光合作用来抵御盐碱胁迫,但都呈现“低促高抑”的现象,说明其具有一定阈值。金丝楸通过调节膜成分、催化活性、类异戊二烯代谢和生物合成过程、苯丙素生物合成、淀粉和蔗糖代谢、植物激素信号转导等生物过程和代谢途径,并结合有关转录因子共同响应盐碱胁迫。本研究为深入研究楸树耐盐碱生理机制和分子机制提供科学的理论依据。

Physiological and Transcriptomic Analysis of Catalpa bungei Seedlings in Response to Saline-alkali Stresses

Objective To explore the physiological and molecular mechanism of saline-alkali tolerance in Catalpa bungei, we studied the influence of different saline-alkali stress on the growth, photosynthetic and physiological indicators of C. bungei seedlings combing with transcriptome sequencing. Methods Pot experiment was used to study the different responses of biomass, photosynthetic and physiological indicators of C. bungei seedlings to different saline-alkali stress. Illumina high-throughput sequence technology was used to sequence the transcriptome, and the effect of saline-alkali stress on transcriptional level was analyzed by bioinformatics. Results Under different saline-alkali stress, the damage degree of leaves was Na2CO3>mixed saline-alkali>NaCl. Net growth of plant height and stem diameter, fresh weight and dry weight of overground part and root, biomass, root-shoot ratio were all significantly suppressed with increasing saline-alkali concentration. But the growth stress index decreased with increasing concentration. Contents of MDA and relative conductivity both rose to varying degrees with increasing concentration. SOD enzymatic activity, contents of soluble sugar and Pro, contents of total chlorophyll and photosynthetic rate increased firstly and decreased then with increasing concentration. Transcriptome sequencing generated a total of 60.4 Gb of raw data. Finally, we obtained 55 793 Unigenes after assembling, of which 29 534 (52.93%) Unigeneswere annotated. Through differentially expressed genes (DEGs) analysis, 1 779, 2 835 and 4 059 DEGs were screened from three comparison groups (CK vs NaCl, CK vs Na2CO3 and CK vs mixed saline-alkali) respectively. GO functional enrichment analysis of these DEGs indicated that they were significantly enriched in integral component of membrane, intrinsic component of membrane, catalytic activity, isoprenoid metabolic and biosynthetic process, oxidoreductase activity. KEGG functional enrichment analysis of these DEGs indicated that they were significantly enriched in phenylpropanoid biosynthesis, starch and sucrose metabolism, plant hormone signal transduction, terpenoid backbone biosynthesis and arginine biosynthesis. Moreover, the most abundant differentially expressed transcription factors (TFs) were bHLH, ERF, MYB-related, NAC, C2H2, WRKY, MYB and bZIP families. Conclusion C. bungei mainly resists from saline-alkali stress by accumulating contents of soluble sugars and Pro, improving SOD enzymatic activity and photosynthesis, but all of them show the phenomenon of low promotion and high suppression, indicating that it has a certain threshold value. C. bungei common responses to saline-alkali stress by regulating biological processes and metabolic pathways including component of membrane, catalytic activity, isoprenoid metabolic and biosynthetic process, phenylpropanoid biosynthesis, starch and sucrose metabolism, plant hormone signal transduction, and interacting with TFs. This study provides a scientific theoretical basis for deeply studying the physiological and molecular mechanisms of saline-alkali tolerance in C. bungei.