Abstract
Polyamines (PAs) play an important regulatory role in many basic cellular processes and physiological and biochemical processes. However, there are few studies on the identification of PA biosynthesis and metabolism family members and the role of PAs in the transition of plant embryogenic calli (EC) into globular embryos (GE), especially in perennial woody plants. We identified 20 genes involved in PA biosynthesis and metabolism from the third-generation genome of longan (Dimocarpus longan Lour.). There were no significant differences between longan and other species regarding the number of members, and they had high similarity with Citrus sinensis. Light, plant hormones and a variety of stress cis-acting elements were found in these family members. The biosynthesis and metabolism of PAs in longan were mainly completed by DlADC2, DlSAMDC2, DlSAMDC3, DlSPDS1A, DlSPMS, DlCuAOB, DlCuAO3A, DlPAO2 and DlPAO4B. In addition, 0.01 mmol∙L−1 1-aminocyclopropane-1-carboxylic acid (ACC), putrescine (Put) and spermine (Spm), could promote the transformation of EC into GE, and Spm treatment had the best effect, while 0.01 mmol∙L−1 D-arginine (D-arg) treatment inhibited the process. The period between the 9th and 11th days was key for the transformation of EC into GE in longan. There were higher levels of gibberellin (GA), salicylic acid (SA) and abscisic acid (ABA) and lower levels of indole-3-acetic acid (IAA), ethylene and hydrogen peroxide (H2O2) in this key period. The expression levels in this period of DlADC2, DlODC, DlSPDS1A, DlCuAOB and DlPAO4B were upregulated, while those of DlSAMDC2 and DlSPMS were downregulated. These results showed that the exogenous ACC, D-arg and PAs could regulate the transformation of EC into GE in longan by changing the content of endogenous hormones and the expression levels of PA biosynthesis and metabolism genes. This study provided a foundation for further determining the physicochemical properties and molecular evolution characteristics of the PA biosynthesis and metabolism gene families, and explored the mechanism of PAs and ethylene for regulating the transformation of plant EC into GE.
Highlights
Polyamines (PAs) are low molecular weight aliphatic nitrogenous bases with biological activity, widely existing in plants, animals and microorganisms [1]
We examined the physicochemical properties of PA biosynthesis and its metabolism proteins, including determining the number of amino acids, as well as the molecular weight (MW), isoelectric point, instability index (II), aliphatic index (AI) and hydropathicity using ExPASy
A total of 20 genes involved in PA biosynthesis and metabolism were identified in the longan third-generation genome, including a member of the arginine decarboxylase (ADC) gene family (DlADC), a member of the ornithine decarboxylase (ODC) gene family (DlODC), three members of the S-adenosylmethionine decarboxylase (SAMDC) gene family (DlSAMDC), two members of the spermidine synthase (SPDS) gene family (DlSPDS), a member of the Spm synthase (SPMS) gene family (DlSPMS), eight members of the copper ammonia oxidase (CuAO) gene family (DlCuAO) and four members of the PA oxidase (PAO) gene family (DlPAO)
Summary
Polyamines (PAs) are low molecular weight aliphatic nitrogenous bases with biological activity, widely existing in plants, animals and microorganisms [1]. The main PAs with important physiological functions in plants are putrescine (Put), spermidine (Spd) and spermine (Spm), which are found in cells as free amines or as amide conjugates [2]. PAs are involved in many physiological and biochemical processes, such as xylem formation, organ development and senescence, seed formation, fruit ripening, etc. PAs are the important stress response factors, and are widely involved in a variety of biotic and abiotic stress responses in plants [8]. Their signal pathways are directly or indirectly related to many metabolic pathways in plants
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