Green Sperm. Identification of Male Gamete Promoters in Arabidopsis

Abstract

Previously, in an effort to better understand the male contribution to fertilization, we completed a maize (Zea mays) sperm expressed sequence tag project. Here, we used this resource to identify promoters that would direct gene expression in sperm cells. We used reverse transcription-polymerase chain reaction to identify probable sperm-specific transcripts in maize and then identified their best sequence matches in the Arabidopsis (Arabidopsis thaliana) genome. We tested five different Arabidopsis promoters for cell specificity, using an enhanced green fluorescent protein reporter gene. In pollen, the AtGEX1 (At5g55490) promoter is active in the sperm cells and not in the progenitor generative cell or in the vegetative cell, but it is also active in ovules, roots, and guard cells. The AtGEX2 (At5g49150) promoter is active only in the sperm cells and in the progenitor generative cell, but not in the vegetative cell or in other tissues. A third promoter, AtVEX1 (At5g62580), was active in the vegetative cell during the later stages of pollen development; the other promoters tested (At1g66770 and At1g73350) did not function in pollen. Comparisons among GEX1 and GEX2 homologs from maize, rice (Oryza sativa), Arabidopsis, and poplar (Populus trichocarpa) revealed a core binding site for Dof transcription factors. The AtGEX1 and AtGEX2 promoters will be useful for manipulating gene expression in sperm cells, for localization and functional analyses of sperm proteins, and for imaging of sperm dynamics as they are transported in the pollen tube to the embryo sac.

Intercellular communication in Arabidopsis thaliana pollen discovered via AHG3 transcript movement from the vegetative cell to sperm

“…However, transcriptome studies of isolated sperm cells showed that sperm cells contain thousands of transcripts, consistent with transcriptional activity (13,30). This idea is supported by the identification of several sperm cell-specific genes, such as GEX1 and DUO1 (31,32). Nevertheless, the extent of active transcription in plant sperm cells remains to be investigated, because some transcripts identified in the sperm cell transcriptome might have been transported from the vegetative cell during pollen development.…”

A genome-wide analysis of SWEET gene family in cotton and their expressions under different stresses

“…GhSWEET1a_At/Dt, GhSWEET2a_At/Dt, GhSWEET5_At/ Dt,GhSWEET7a_At/Dt, GhSWEET9_At/Dt, GhSWEET15-c_At/Dt highly expressed in floral organs, indicating different members of the GhSWEETs family in cotton expressed in different parts of the flower and in different developmental stages. AtSWEET1/4/5/7/8, AtSWEET13/14/ 15 have a relatively high level of expression in floral organs of Arabidopsis (Feng et al 2015;Engel et al 2005;47 Wellmer et al 2006). OsSWEET1a/2a/3a/4/5/15 in rice also showed relatively high expression levels at different developmental stages of flowers and panicles (Feng et al 2015).…”

Cis-Regulatory Elements Determine Germline Specificity and Expression Level of an Isopentenyltransferase Gene in Sperm Cells of Arabidopsis

“…The highly conserved GCS1/ HAP2 gene encoding a secreted membrane protein is essential for fertilization in a myriad of other eukaryotes as well (Mori et al, 2006;von Besser et al, 2006;Liu et al, 2008). Additional male gamete-selective genes have been identified and characterized in lily and Arabidopsis (Engel et al, 2005;Okada et al, 2005aOkada et al, , 2005bBrownfield et al, 2009aBrownfield et al, , 2009b.…”

“…Another lily gene, GCS1, and its Arabidopsis homolog HAP2 are expressed in sperm cells and are essential for fertilization (Mori et al, 2006;von Besser et al, 2006). Sperm cell-expressed genes GAMETE EXPRESSED 1 (GEX1) and GEX2 were identified in maize sperm cell-specific transcripts, and homologous Arabidopsis genes were designated AtGEX1 and AtGEX2 (Engel et al, 2005). AtGEX1 is expressed in sperm cells of mature pollen in Arabidopsis.…”