Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, 210014, China.
Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Nanjing, 210014, China.
Mol Biol Rep. 2024 Sep 28;51(1):1025. doi: 10.1007/s11033-024-09957-w.
Hydroxynitrile lyases (HNLs) are a class of hydrolytic enzymes from a wide range of sources, which play crucial roles in the catalysis of the reversible conversion of carbonyl compounds derived from cyanide and free cyanide in cyanogenic plant species. HNLs were also discovered in non-cyanogenic plants, such as Arabidopsis thaliana, and their roles remain unclear even during plant growth and reproduction.
The pattern of expression of the HNL in A. thaliana (AtHNL) in different tissues, as well as under abiotic stresses and hormone treatments, was examined by real-time quantitative reverse transcription PCR (qRT-PCR) and an AtHNL promoter-driven histochemical β-glucuronidase (GUS) assay. AtHNL is highly expressed in flowers and siliques, and the expression of AtHNL was dramatically affected by abiotic stresses and hormone treatments. The overexpression of AtHNL resulted in transgenic A. thaliana seedlings that were more tolerance to mannitol and salinity. Moreover, transgenic lines of A. thaliana that overexpressed this gene were less sensitive to abscisic acid (ABA). Altered expression of ABA/stress responsive genes was also observed in hnl mutant and AtHNL-overexpressing plants, suggesting AtHNL may play functional roles on regulating Arabidopsis resistance to ABA and abiotic stresses by affecting ABA/stress responsive gene expression. In addition, the overexpression of AtHNL resulted in earlier flowering, whereas the AtHNL mutant flowered later than the wild type (WT) plants. The expression of the floral stimulators CONSTANS (CO), SUPPRESSOR OF OVER EXPRESSION OF CO 1 (SOC1) and FLOWERING LOCUS T (FT) was upregulated in plants that overexpressed AtHNL when compared with the WT plants. In contrast, expression of the floral repressor FLOWERING LOCUS C (FLC) was upregulated in AtHNL mutants and downregulated in plants that overexpressed AtHNL compared to the WT plants.
This study revealed that AtHNL can be induced under abiotic stresses and ABA treatment, and genetic analysis showed that AtHNL could also act as a positive regulator of abiotic stress and ABA tolerance, as well as flowering time.
羟腈裂解酶（HNLs）是一类来源广泛的水解酶，在催化氰源植物中羰基化合物及其游离氰化物的可逆转化中发挥着关键作用。在非氰源植物如拟南芥中也发现了 HNLs，但其作用在植物生长和繁殖过程中仍不清楚。
通过实时定量逆转录 PCR（qRT-PCR）和 HNL 启动子驱动的组织化学β-葡萄糖醛酸酶（GUS）测定，检测 HNL 在拟南芥不同组织中的表达模式，以及在非生物胁迫和激素处理下的表达模式。AtHNL 在花和蒴果中高度表达，AtHNL 的表达受非生物胁迫和激素处理的显著影响。AtHNL 的过表达导致拟南芥幼苗对甘露醇和盐胁迫的耐受性增强。此外，过表达该基因的拟南芥转基因株系对脱落酸（ABA）的敏感性降低。在 hnl 突变体和 AtHNL 过表达植物中也观察到 ABA/胁迫应答基因的表达发生改变，表明 AtHNL 可能通过影响 ABA/胁迫应答基因的表达，在调节拟南芥对 ABA 和非生物胁迫的抗性方面发挥功能作用。此外，AtHNL 的过表达导致开花提前，而 AtHNL 突变体的开花时间晚于野生型（WT）植物。与 WT 植物相比，过表达 AtHNL 的植物中花刺激物 CONSTANS（CO）、SUPPRESSOR OF OVER EXPRESSION OF CO 1（SOC1）和 FLOWERING LOCUS T（FT）的表达上调，而花抑制物 FLOWERING LOCUS C（FLC）的表达在 AtHNL 突变体中上调，在过表达 AtHNL 的植物中下调。
本研究表明，AtHNL 可在非生物胁迫和 ABA 处理下诱导，遗传分析表明，AtHNL 还可作为非生物胁迫和 ABA 耐受以及开花时间的正调控因子。
