Effects of Natural Variation on Pollen Tube Sensitivity to Synergid Signals

Communication between the male gametophyte (the tip-growing pollen tube) and the female gametophyte (the synergid cells) is crucial for sexual reproduction in flowering plants. The reception of the pollen tube (PT) depends on its recognition and sensitivity to the signals from the synergid cells for its rupture, sperm release, and double fertilization. Mutations in genes regulating communication between the synergid cells and pollen tube lead to PT overgrowth. Despite significant advances in understanding the molecular mechanism of pollen tube reception in Arabidopsis, there remains a need for more comprehensive information on the impact of natural variations on physiological traits related to pollen tube and synergid signals in pollen tube reception. This research investigates the effects of natural variation on pollen tube sensitivity to synergid signals mediated by NORTIA. In nortia homozygous mutants, PT-synergid communication is disrupted due to lower levels of calcium signals in the synergid cells, resulting in PT overgrowth. Using the Aniline blue staining procedure, this study identified twelve ecotypes of Arabidopsis thaliana out of the twenty-four ecotypes that could suppress the PT overgrowth phenotype of nta-1. I observed that the suppressor ecotypes exhibit characteristics like the Columbia (Col-0) ecotype, while non-suppressor ecotypes resemble the Ws-2 ecotype. Comparing the impact of the Columbia (Col-0) and Wassilewskija (Ws-2) ecotypes on PT overgrowth in the nta-2 mutant revealed that Columbia (Col-0) effectively suppressed PT overgrowth compared to Wassilewskija (Ws-2). We investigated the sensitivity of PT integrity mutants to synergid signals. Our results showed that compromised PT integrity mutant genes (mlo1mlo15) partially suppressed PT overgrowth in nta-1. I propose that suppressor ecotypes and mutants may exhibit a heightened sensitivity to synergid signals, that help them to regulate their response to synergid signals finely.