Transcriptomic profiling of genes in matured dimorphic seeds of euhalophyte Suaeda salsa

Abstract

Background Suaeda salsa (S. salsa) is a euhalophyte with high economic value. S. salsa can produce dimorphic seeds. Brown seeds are more salt tolerant, can germinate quickly and maintain the fitness of the species under high saline conditions. Black seeds are less salt tolerant, may become part of the seed bank and germinate when soil salinity is reduced. Previous reports have mainly focused on the ecophysiological traits of seed germination and production under saline conditions in this species. However, there is no information available on the molecular characteristics of S. salsa dimorphic seeds.ResultsIn the present study, a total of 5825 differentially expressed genes were obtained; and 4648 differentially expressed genes were annotated based on a sequence similarity search, utilizing five public databases by transcriptome analysis. The different expression of these genes may be associated with embryo development, fatty acid, osmotic regulation substances and plant hormones in brown and black seeds. Compared to black seeds, most genes may relate to embryo development, and various genes that encode fatty acid desaturase and are involved in osmotic regulation substance synthesis or transport are upregulated in brown seeds. A large number of differentially expressed genes related to plant hormones were found in brown and black seeds, and their possible roles in regulating seed dormancy/germination were discussed.ConclusionsUpregulated genes involved in seed development and osmotic regulation substance accumulation may relate to bigger seed size and rapid seed germination in brown seeds, compared to black seeds. Differentially expressed genes of hormones may relate to seed dormancy/germination and the development of brown and black seeds. The transcriptome dataset will serve as a valuable resource to further understand gene expression and functional genomics in S. salsa dimorphic seeds.Electronic supplementary materialThe online version of this article (10.1186/s12864-017-4104-9) contains supplementary material, which is available to authorized users.

Adaptation of Halophytes to Different Habitats

“…Xu et al found that the content in Na + , K + , Cl − , and Ca 2+ were higher in brown seed compared to black, as well as a higher activity of relative transporters in brown seeds [e.g., vacuolar Na + / H + antiporter (NHX), potassium transporter (HAK), chloride channel protein (CLC), Ca 2+ /H + antiporter, and tonoplast (CAX)], which could explain the better germination rate. These mechanisms are involved in maintaining ionic homeostasis and improve water uptake for seeds during germination under salt stress [30].…”

“…An expression analysis of betaine aldehyde dehydrogenase gene (SsBADH) in S. salsa showed that brown seeds have higher expression of this gene, and exhibit better germination compared with black seeds. Also, larger brown seeds register a greater increase in sugar facilitating a rapid germination [30].…”

“…Low germination may be related to higher ABA sensitivity rather than the difference in ABA content among dimorphic seeds in S. salsa [43]. Other hormones, such as ethylene, may promote seed germination through the antagonism of ABA signaling, and brassinosteroids may also interact with other hormones to influence seed dormancy by reducing ABA sensitivity and thereby increasing germination [30].…”

“…Xu et al realized transcriptomic profiling of genes in matured dimorphic seeds of euhalophyte Suaeda salsa ( Table 5). Upregulated genes involved in seed development, accumulation of osmolytes, and differentially expressed genes of hormones may relate to seed dormancy/germination, and to bigger size and rapid seed germination in brown seeds, compared to black seeds [30].…”

Seed Heteromorphism: An Important Adaptation of Halophytes for Habitat Heterogeneity

“…Halophytes can produce salt tolerant seeds with more betain and can ensure good seed germination under salt stress ( Tanveer and Shah, 2017 ). Expression analysis of betaine aldehyde dehydrogenase gene ( SsBADH ) in S. salsa showed that brown seeds have higher expression of SsBADH and exhibit better seed germination as compared with black seeds ( Xu et al, 2017 ). Proline is generally regarded as another important osmoregulator ( Flowers and Colmer, 2008 ), nonetheless studies showed that proline also acts as signaling compound, which induces delayed germination process by keeping embryo in resting state under stress conditions ( Thakur and Sharma, 2005 ).…”