背景:小孢子胚胎发生是一个非常复杂的过程,由生理和分子因素的复合网络综合调节,其中激素是最关键的因素之一。生长素是应力诱导的小孢子重编程所必需的,然而,其对小孢子胚胎发生的调控机制尚不清楚。
结果:在这项研究中,我们发现在五彩芽上外源喷施100mg·L-1IAA显着提高了小孢子胚胎发生的速率,而且加速了胚胎发生的过程。生理生化试验表明,氨基酸的含量,可溶性总糖,可溶性蛋白质,IAA处理后,淀粉显著增加。此外,外源性喷施100mg·L-1IAA显著增强IAA,GA4和GA9内容,过氧化氢酶(CAT)和丙二醛(MDA)活性增加,和减少脱落酸(ABA),MDA和可溶性原凝集素含量,芽中H2O2和O2·-的生产率,具有最大的晚期无核小孢子种群。对分别用100mg·L-1IAA和淡水处理的芽进行转录组测序。总共确定了2004年的DEG,其中79个参与微孔发育,胚胎发育和细胞壁形成和修饰,其中大部分被上调。KEGG和GO分析显示9.52%的DEGs富集在植物激素合成和信号转导通路中,戊糖和葡萄糖醛酸交换途径,和氧化磷酸化途径。
结论:这些发现表明外源性IAA改变了内源性激素的含量,总可溶性糖,氨基酸,淀粉,可溶性蛋白质,MDA和原果胶,CAT和过氧化物酶(POD)的活性,以及H2O2和O2·-的产生速率。结合转录组分析,发现大多数基因与赤霉素(GA)和生长素(IAA)的合成和信号转导有关,果胶甲基化酶(PME)和多聚半乳糖醛酸酶(PGs)基因以及与ATP合成和电子传递链相关的基因被上调,与ABA合成和信号转导相关的基因下调。这些结果表明,外源性IAA处理可以改变内源性激素的平衡,加速细胞壁降解,促进ATP合成和养分积累,抑制ROS积累,最终促进小孢子胚胎发生。
BACKGROUND: Microspore embryogenesis is an extraordinarily complicated process, comprehensively regulated by a composite network of physiological and molecular factors, among which hormone is one of the most crucial factors. Auxin is required for stress-induced microspore reprogramming, however, the mechanism of its regulation of microspore embryogenesis is still unclear.
RESULTS: In this study, we found exogenously spraying 100 mg·L- 1 IAA on the buds of Wucai significantly increased the rate of microspore embryogenesis, and moreover accelerated the process of embryogenesis. Physiological and biochemical tests showed that the contents of amino acids, soluble total sugar, soluble protein, and starch were significantly increased after IAA treatment. Furthermore, exogenously spraying 100 mg·L- 1 IAA significantly enhanced IAA, GA4, and GA9 content, increased catalase (CAT) and malondialdehyde (MDA) activity, and reduced abscisic acid (ABA), MDA and soluble protopectin content, H2O2 and O2·- production rate in the bud with the largest population of late-uninucleate-stage microspores. Transcriptome sequencing was performed on buds respectively treated with 100 mg·L- 1 IAA and fresh water. A total of 2004 DEGs were identified, of which 79 were involved in micropores development, embryonic development and cell wall formation and modification, most of which were upregulated. KEGG and GO analysis revealed that 9.52% of DEGs were enriched in plant hormone synthesis and signal transduction pathways, pentose and glucuronic acid exchange pathways, and oxidative phosphorylation pathways.
CONCLUSIONS: These findings indicated that exogenous IAA altered the contents of endogenous hormone content, total soluble sugar, amino acid, starch, soluble protein, MDA and protopectin, the activities of CAT and peroxidase (POD), and the production rate of H2O2 and O2·-. Combined with transcriptome analysis, it was found that most genes related to gibberellin (GA) and Auxin (IAA) synthesis and signal transduction, pectin methylase (PME) and polygalacturonase (PGs) genes and genes related to ATP synthesis and electron transport chain were upregulated, and genes related to ABA synthesis and signal transduction were downregulated. These results indicated that exogenous IAA treatment could change the balance of endogenous hormones, accelerate cell wall degradation, promote ATP synthesis and nutrient accumulation, inhibit ROS accumulation, which ultimately promote microspore embryogenesis.