Gametophyte interaction and sexual reproduction: how plants make a zygote

Abstract

The evolutionary success of higher plants relies on a very short gametophytic phase, which underlies the sexual reproduction cycle. Sexual plant reproduction takes place in special organs of the flower: pollen, the male gametophyte, is released from the anthers and then adheres, grows and interacts along various tissues of the female organs, collectively known as the pistil. Finally, it fertilizes the female gametophyte, the embryo sac. Pollen is released as bi or tricellular, highly de-hydrated and presumably containing all the biochemical components and transcripts to germinate. Upon hydration on the female tissues, it develops a cytoplasmic extension, the pollen tube, which is one of the fastest growing cells in nature. Pollen is completely "ready-to-go", but despite this seemingly simple reaction, very complex interactions take place with the female tissues. In higher animals, genetic mechanisms for sex determination establish striking developmental differences between males and females. In contrast, most higher plant species develop both male and female structures within the same flower, allowing self-fertilization. Outcrossing is ensured by self-incompatibility mechanisms, which evolved under precise genetic control, controlling self-recognition and cell-to-cell interaction. Equally important is pollen selection along the female tissues, where interactions between different cell types with inherent signalling properties correspond to check-points to ensure fertilization. Last but not least, pollen-pistil interaction occurs in a way that enables the correct targeting of the pollen tubes to the receptive ovules. In this review, we cover the basic mechanisms underlying sexual plant reproduction, from the structural and cellular determinants, to the most recent genetic advances.

Transmission ratio distortion in Arabidopsis lyrata: effects of population divergence and the S-locus

“…There could also have been selection for particular allele combinations during gamete formation of the two different F 1 parents. Interactions between pollen and stigma-leading to fertilization-are also known to be complicated (for example, reviewed by Chaudhury et al, 2001;Boavida et al, 2005). Pollen performance can vary between different genotypes and might lead to nonrandom fertilization (Snow and Spira, 1991).…”

Sperm Proteasome as a Putative Egg Coat Lysin in Mammals

“…Similar to animal spermatozoon, pollen, the male gametophyte, is a highly specialized structure, consisting of two or three cells. Pollen is released from the anthers and adheres to the surface of the female stigma, equipped with a cytoplasmic extension known as the pollen tube (Boavida et al 2005 ). The pollen tube rapidly grows through the style to the ovules (Boavida et al 2005 ).…”

“…Pollen is released from the anthers and adheres to the surface of the female stigma, equipped with a cytoplasmic extension known as the pollen tube (Boavida et al 2005 ). The pollen tube rapidly grows through the style to the ovules (Boavida et al 2005 ). Pollen tube adhesion and growth guides the pollen toward the ovary where it fertilizes the embryo sac, the female gametophyte (Boavida et al 2005 ).…”

“…The pollen tube rapidly grows through the style to the ovules (Boavida et al 2005 ). Pollen tube adhesion and growth guides the pollen toward the ovary where it fertilizes the embryo sac, the female gametophyte (Boavida et al 2005 ). For a more in-depth account of fertilization in higher plants, please refer to the review by Boavida et al ( 2005 ).…”

“…Pollen tube adhesion and growth guides the pollen toward the ovary where it fertilizes the embryo sac, the female gametophyte (Boavida et al 2005 ). For a more in-depth account of fertilization in higher plants, please refer to the review by Boavida et al ( 2005 ). Evolutionary conservation of the components and roles of the UPS appear to reach beyond the animal kingdom to plants, where pollen adhesion and guidance seem to depend on ubiquitin.…”