Abstract
Saururus chinensis is a core member of Saururaceae, a perianthless (lacking petals or sepals) family. Due to its basal phylogenetic position and unusual floral composition, study of this plant family is important for understanding the origin and evolution of perianthless flowers and petaloid bracts among angiosperm species. To isolate genes involved in S. chinensis flower development, subtracted floral cDNA libraries were constructed by using suppression subtractive hybridization (SSH) on transcripts isolated from developing inflorescences and seedling leaves. The subtracted cDNA libraries contained a total of 1,141 ESTs and were used to create cDNA microarrays to analyze transcript profiles of developing inflorescence tissues. Subsequently, qRT-PCR analyses of eight MADS-box transcription factors and in situ hybridizations of two B-class MADS-box transcription factors were performed to verify and extend the cDNA microarray results. Finally, putative phylogenetic relationships within the B-class MADS-box gene family were determined using the discovered S. chinensis B-class genes to compare K-domain sequences with B genes from other basal angiosperms. Two hundred seventy-seven of the 1,141 genes were found to be expressed differentially between S. chinensis inflorescence tissues and seedling leaves, 176 of which were grouped into at least one functional category, including transcription (14.75%), energy (12.59%), metabolism (9.12%), protein-related function (8.99%), and cellular transport (5.76%). qRT-PCR and in situ hybridization of selected MADS-box genes supported our microarray data. Phylogenetic analysis indicated that a total of six B-class MADS-box genes were isolated from S. chinensis. The differential regulation of S. chinensis B-class MADS-box transcription factors likely plays a role during the development of subtending bracts and perianthless flowers. This study contributes to our understanding of inflorescence development in Saururus, and represents an initial step toward understanding the formation of petaloid bracts in this species.
Highlights
The morphological diversity of angiosperm flowers represents a breathtaking exposition of the power of evolution
Given that genomic information was lacking in the Saururaceae, the EST library construction and expression analyses described here provide an important contribution to the floral developmental genetics of paleoherb species
The analysis of our suppression subtractive hybridization (SSH) results indicated that our procedure was successful in isolating transcripts involved in S. chinensis flower development
Summary
The morphological diversity of angiosperm flowers represents a breathtaking exposition of the power of evolution. Through a process known as the ABCE model of floral morphogenesis, combinations of transcription factor proteins specify organ identities in developing flowers, typically leading to the outgrowth of sepals, petals, stamens and pistils [1,2,3]. In the ABCE model, Atype transcription factors specify the respective identities of the first and second whorl organs, i.e., the sepals and petals. E-class genes combine with A, B or C genes to specify organ identities [3,8,9]. In Arabidopsis thaliana, there are two A genes, APETALA1 (AP1) and APETALA2 (AP2), two B genes, APETALA3 (AP3) and PISTIL-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
