Sporophytic control of pollen tube growth and guidance in maize

Abstract

Pollen tube germination, growth, and guidance (progamic phase) culminating in sperm discharge is a multi-stage process including complex interactions between the male gametophyte as well as sporophytic tissues and the female gametophyte (embryo sac), respectively. Inter- and intra-specific crossing barriers in maize and Tripsacum have been studied and a precise description of progamic pollen tube development in maize is reported here. It was found that pollen germination and initial tube growth are rather unspecific, but an early, first crossing barrier was detected before arrival at the transmitting tract. Pollination of maize silks with Tripsacum pollen and incompatible pollination of Ga1s/Ga1s-maize silks with ga1-maize pollen revealed another two incompatibility barriers, namely transmitting tract mistargeting and insufficient growth support. Attraction and growth support by the transmitting tract seem to play key roles for progamic pollen tube growth. After leaving transmitting tracts, pollen tubes have to navigate across the ovule in the ovular cavity. Pollination of an embryo sac-less maize RNAi-line allowed the role of the female gametophyte for pollen tube guidance to be determined in maize. It was found that female gametophyte controlled guidance is restricted to a small region around the micropyle, approximately 50–100 μm in diameter. This area is comparable to the area of influence of previously described ZmEA1-based short-range female gametophyte signalling. In conclusion, the progamic phase is almost completely under sporophytic control in maize.

New insights into the functional roles of reactive oxygen species during embryo sac development and fertilization inArabidopsis thaliana

“…Chemoattractants located in the pistil are thought to guide pollen tubes toward the ovules. [43][44][45] Recent reports showed that female gametophytes respond to stigma pollination or pollen tube growth through the female transmitting track, supporting the existence of long distance signaling pathways. The expression of the AMC gene, named after the abstinence by mutual consent mutant, encodes a peroxin required for protein import into peroxisomes and essential for pollen tube discharge, is induced in the embryo sac by pollen deposition on the stigma.…”

Efficient plant male fertility depends on vegetative nuclear movement mediated by two families of plant outer nuclear membrane proteins

“…Unlike animals, which have sperm cells (SCs) that travel through self-propelled flagellum, flowering plants use pollen tubes to deliver SCs to ovules (10)(11)(12)(13). In Arabidopsis, pollen tube growth is guided by chemical cues in carpel tissues and attracted by small peptides secreted by synergid cells in the vicinity of ovules (14)(15)(16)(17)(18).…”

Female gametophyte development and double fertilization in Balsas teosinte, Zea mays subsp. parviglumis (Poaceae)

“…Subsequently, ovaries were immersed in 5% NaOH overnight and then, rinsed with distilled water and 50 mM KPO 4 . They were stained with 0.01% decolorized aniline blue in 50 mM KPO 4 for 20 min (Lausser et al 2010) and observed under UV using a Zeiss Axiophot epifluorescence microscope.…”

“…Pollen tube growth in maize has been well studied (Adams and Mackay 1953;Kiesselbach 1980;Heslop-Harrison et al 1985;Styles 1987;Kliwer and Dresselhaus 2010;Lausser et al 2010). Germination of pollen grains and the growth of pollen tubes of Balsas teosinte are generally similar to those of maize.…”