Understanding plant reproduction offers potential routes to impact seed crop agriculture and reveal key principles of plant cell. Cell-cell signalling during plant reproduction revolves around the interactions between a small family of receptor-like kinases, their co-receptors, and ligands. Several specific peptides and carbohydrates have recently been confirmed as ligands in reproductive signalling, opening new avenues to investigate their interactions and potentially distinct downstream effects.1

The multistep controls of pollen tube guidance can be divided into two phases: pre-ovular and ovular guidance. During preovular guidance various molecules such as Exo70A1 and Chemocyanin, in style and transmitting tract GABA and D-serine, etc., controls the activity of pollen germination and provide the support for pollen tube growth towards the ovary where the ovules are located. Ovular guidance refers to the pollen tube guidance after entering the ovary, the pollen tube receives directional cues mainly from FERONIA, LORELEI, ZmEA1(Maize), LURE(Arabidopsis), etc., localized in synergid cells and regulation to terminate growth once a pollen tube arrives at the target ovules.2

In Arabidopsis thaliana, the sirene pistils and wild type of embryo sac structure was studied using Normarski and CLSM microscopy to understand female control of male gamete delivery during fertilization. The Reciprocal cross conducted between heterozygous sirene a (srn/SRN) and wild type plants indicated the sirene is a strict embryo sac mutation. Three models were developed based on observations. In the first model, the sirene embryo sac would be structurally or physiologically incapable of correctly receiving pollen tube. In the second model, the sirene embryo sac would not correctly emit signals that are required either for the arrest of pollen tube growth or for pollen tube discharge and in the last model, the sirene embryo sac would be defective in the perception or transduction of pollen tube that leads to structural or physiological changes in embryo sac necessary for pollen tube growth.3

The pollen pistil interaction by aniline blue technique between direct and reciprocal of two species of Sesamum indicum (CO 1, VRI 3, TMV 7) and Sesamum radiatum indicated due to some inhibitory activity for pollen germination on stigmatic surface and pollen tube development along style depicting the presence of fertilization barrier and hence capsules were not developed. The frequency of pollen germination and pollen tube growth was very slow in interspecific cross among two species.4

Overall, Signalling between sexes during pollen tube reception is crucial for the reproductive success which promotes outcrossing and prevents self-fertilization, and it also helps in maintaining genetic diversity within plant populations which is essential for the long-term survival and evolutionary success of species, as it provides the raw material for natural selection to act upon.

References:

1BAILLIE, A. L., SLOAN, J., QU, L. J. AND SMITH, L. M., 2023, Signalling between the sexes during pollen tube reception. Trends Plant Sci., 29(3): 343-354.

2DRESSELHAUS, T. AND FRANKLIN-TONG, N., 2013, Male–female crosstalk during pollen germination, tube growth and guidance, and double fertilization. Mol. Plant, 6(4):1018-1036.

3ROTMAN, N., ROZIER, F., BOAVIDA, L., DUMAS, C., BERGER, F. AND FAURE, J. E., 2003, Female control of male gamete delivery during fertilization in Arabidopsis thaliana. Curr. Biol., 13(5):432-436.

4SRUTHI, S.R., KALAIYARASI, R., SASIKALA, R. AND SUDHA, M., 2022, Pollen pistil interaction in the interspecific cross of Sesamum indicum and S. radiatum. Electron. J. Plant Breed., 13(4): 1288-1296.