Smolikova Galina, Strygina Ksenia, Krylova Ekaterina, Vikhorev Aleksander, Bilova Tatiana, Frolov Andrej, Khlestkina Elena, Medvedev Sergei
Department of Plant Physiology and Biochemistry, St. Petersburg State University, 199034 St. Petersburg, Russia.
Postgenomic Studies Laboratory, Federal Research Center N.I. Vavilov All-Russian Institute of Plant Genetic Resources of Russian Academy of Sciences, 190000 St. Petersburg, Russia.
Plants (Basel). 2022 Jun 25;11(13):1686. doi: 10.3390/plants11131686.
The seed-to-seedling transition is a crucial step in the plant life cycle. The transition occurs at the end of seed germination and corresponds to the initiation of embryonic root growth. To improve our understanding of how a seed transforms into a seedling, we germinated the L. seeds for 72 h and divided them into samples before and after radicle protrusion. Before radicle protrusion, seeds survived after drying and formed normally developed seedlings upon rehydration. Radicle protrusion increased the moisture content level in seed axes, and the accumulation of ROS first generated in the embryonic root and plumule. The water and oxidative status shift correlated with the desiccation tolerance loss. Then, we compared RNA sequencing-based transcriptomics in the embryonic axes isolated from pea seeds before and after radicle protrusion. We identified 24,184 differentially expressed genes during the transition to the post-germination stage. Among them, 2101 genes showed more prominent expression. They were related to primary and secondary metabolism, photosynthesis, biosynthesis of cell wall components, redox status, and responses to biotic stress. On the other hand, 415 genes showed significantly decreased expression, including the groups related to water deprivation (eight genes) and response to the ABA stimulus (fifteen genes). We assume that the water deprivation group, especially three genes also belonging to ABA stimulus (LTI65, LTP4, and HVA22E), may be crucial for the desiccation tolerance loss during a metabolic switch from seed to seedling. The latter is also accompanied by the suppression of ABA-related transcription factors ABI3, ABI4, and ABI5. Among them, HVA22E, ABI4, and ABI5 were highly conservative in functional domains and showed homologous sequences in different drought-tolerant species. These findings elaborate on the critical biochemical pathways and genes regulating seed-to-seedling transition.
种子到幼苗的转变是植物生命周期中的关键步骤。这种转变发生在种子萌发末期，对应着胚根生长的开始。为了更好地理解种子如何转变为幼苗，我们将L.种子萌发72小时，并在胚根突出前后将它们分成样本。在胚根突出之前，种子干燥后仍能存活，并在重新水化后形成正常发育的幼苗。胚根突出增加了种子轴中的水分含量水平，活性氧首先在胚根和胚芽中积累。水分和氧化状态的变化与脱水耐受性的丧失相关。然后，我们比较了胚根突出前后从豌豆种子中分离出的胚轴基于RNA测序的转录组学。我们在向萌发后阶段的转变过程中鉴定出24184个差异表达基因。其中，2101个基因表现出更显著的表达。它们与初级和次级代谢、光合作用、细胞壁成分的生物合成、氧化还原状态以及对生物胁迫的反应有关。另一方面，415个基因表现出显著下调表达，包括与缺水相关的基因（8个基因）和对脱落酸刺激的反应相关的基因（15个基因）。我们假设缺水组，特别是也属于脱落酸刺激组的三个基因（LTI65、LTP4和HVA22E），可能对种子到幼苗代谢转换过程中的脱水耐受性丧失至关重要。后者还伴随着脱落酸相关转录因子ABI3、ABI4和ABI5的抑制。其中，HVA22E、ABI4和ABI5在功能域上高度保守，并且在不同耐旱物种中显示出同源序列。这些发现阐述了调节种子到幼苗转变的关键生化途径和基因。
