AtNG1 encodes a protein that is required for seed germination

The pentatricopeptide repeat (PPR) family of eukaryotic proteins has numerous members in plants and is important for plant development. In the present study, we cloned a novel PPR gene, designated AtNG1, and characterized the ng1 Arabidopsis mutant. Morphological and structural observation of an ng1 mutant revealed that its sexual reproduction and seed formation processes are essentially normal. The mature embryonic root of ng1 is fully developed and has a well-differentiated structure; however, ng1 seeds cannot germinate, even when supplied with supplemental hormones and nutrition. Further investigation showed that embryo expansion and root cell elongation fails to occur after water imbibitions. Transient gene expression analysis indicated that AtNG1 localizes in mitochondrion. This implies that the deficiency of mitochondrion function might be the reason for the failed seed germination. Thus, our finding confirmed that AtNG1 plays a critical role in the early process of seed germination.     

不同浓度5-氨基乙酰丙酸(ALA)浸种对NaCl胁迫下番茄种子发芽率及芽苗生长的影响

为探讨外源5-氨基乙酰丙酸(ALA)对NaCl胁迫下番茄种子发芽率及芽苗生长的影响,以‘中杂九号’番茄种子为试材,不同浓度ALA(0、0.1、0.5、1.0、5.0、10.0mg/L)浸种24h后,在0、25、50、100mmol/L NaCl胁迫下,28℃,黑暗培养7d,研究ALA对番茄种子发芽参数(发芽率、发芽势、发芽指数、活力指数、芽苗总鲜重)及胚芽和胚根中的抗氧化酶(超氧化物歧化酶SOD、过氧化物酶POD、过氧化氢酶CAT)活性和丙二醛(MDA)含量的影响.结果表明:非盐胁迫下,ALA浸种使番茄种子的发芽势、发芽指数、活力指数、芽苗总鲜重增加,胚根中SOD、POD活性降低,MDA含量减少;25 mmol/L NaCl胁迫能够提高发芽率、活力指数、芽苗总鲜重,而50-100mmol/L NaCl胁迫极显著的降低发芽率、发芽势、发芽指数、活力指数;0.1-0.5mg/L ALA浸种能够提高NaCl胁迫下番茄种子的发芽率、发芽指数、活力指数、芽苗总鲜重和抗氧化酶活性,降低MDA含量,而高浓度ALA(10.0mg/L)浸种导致发芽率、发芽指数、活力指数降低.总之,ALA浸种能够促进番茄种子萌发和芽苗生长,浸种浓度不宜超过5.0mg/L,NaCl胁迫下以0.1 mg/L ALA浸种处理效果最佳.     

OsLOL1, a C2C2‐type zinc finger protein,interacts with OsbZIP58 to promote seed germination through the modulation of gibberellin biosynthesis in Oryza sativa

Seed germination is a key developmental process in the plant life cycle that is influenced by various environmental cues and phytohormones through gene expression and a series of metabolism pathways. In the present study, we investigated a C2C2‐type finger protein, OsLOL1, which promotes gibberellin (GA) biosynthesis and affects seed germination in Oryza sativa (rice). We used OsLOL1 antisense and sense transgenic lines to explore OsLOL1 functions. Seed germination timing in antisense plants was restored to wild type when exogenous GA₃ was applied. The reduced expression of the GA biosynthesis gene OsKO2 and the accumulation of ent‐kaurene were observed during germination in antisense plants. Based on yeast two‐hybrid and firefly luciferase complementation analyses, OsLOL1 interacted with the basic leucine zipper protein OsbZIP58. The results from electrophoretic mobility shift and dual‐luciferase reporter assays showed that OsbZIP58 binds the G‐box cis‐element of the OsKO2 promoter and activates LUC reporter gene expression, and that interaction between OsLOL1 and OsbZIP58 activates OsKO2 gene expression. In addition, OsLOL1 decreased SOD1 gene expression and accelerated programmed cell death (PCD) in the aleurone layer of rice grains. These findings demonstrate that the interaction between OsLOL1 and OsbZIP58 influences GA biosynthesis through the activation of OsKO2 via OsbZIP58, thereby stimulating aleurone PCD and seed germination.     

Interactive effects of salt and alkali stresses on seed germination,germination recovery,and seedling growth of a halophyte Spartina alterniflora (Poaceae)

Soil salinization and alkalinization frequently co-occur in nature, but there is little information on the interactive effects of salt and alkali stresses on plants. Seed germination and early seedling growth are crucial stages for plant establishment. We investigated the interactive effects of salt and alkali stresses on seed germination, germination recovery and seedling growth of a halophyte Spartina alterniflora. Seed germination percentage was not significantly reduced at low salinity (≤ 200 mM) at pH 6.63–9.95, but decreased with increased salinity and pH. Ungerminated seeds germinated well after transfer to distilled water from treatment solutions, indicating that seeds can remain viable in high salt–alkaline habits. Shoot growth was stimulated at low salinity and pH, but decreased with increased salinity and pH. Radicle elongation decreased sharply with increased salinity and pH, and was significantly inhibited when pH ≥ 9.0, indicating that the radicles are very sensitive to salt–alkaline stress. The deleterious effects of salinity or high pH alone were less than when combined. A reciprocal enhancement of salt and alkali stresses is a characteristic feature for salt–alkaline stress. Stepwise regression analysis indicates that salinity is the dominant factor, while pH and buffer capacity are secondary for salt–alkaline mixed stress.