KAKU4-mediated deformation of the vegetative nucleus controls its precedent migration over sperm cells in pollen tubes

Abstract

One table, seven figures, and two supplemental figures. 27 Word count: 3,967 words 28 29 Running title: KAKU4 controls migration of the nucleus in pollen tubes 30 2 Highlight 31The nuclear envelope protein KAKU4 is involved in controlling the migration order of 32 vegetative nuclei and sperm cells in pollen tubes, affecting the competitive ability of 33 pollen for fertilization. 34 35 36 Abstract 37 A putative nuclear lamina protein, KAKU4, modulates nuclear morphology in 38 Arabidopsis thaliana seedlings but its physiological significance is unknown. KAKU4 39 was strongly expressed in mature pollen grains, each of which has a vegetative cell 40 and two sperm cells. KAKU4 protein was highly abundant on the envelopes of 41 vegetative nuclei (VNs) and less abundant on the envelopes of sperm cell nuclei 42 (SCNs) in pollen grains and elongating pollen tubes. VN is irregularly shaped in 43wild-type pollen. However, KAKU4 deficiency caused it to become more spherical. 44 These results suggest that the dense accumulation of KAKU4 is responsible for the 45 irregular shape of the VNs. After a pollen grain germinates, the VN and SCNs migrate 46 to the tip of the pollen tube. In the wild type, the VN preceded the SCNs in 91-93% of 47 the pollen tubes, whereas in kaku4 mutants, the VN trailed the SCNs in 39-58% of the 48 pollen tubes. kaku4 pollen was less competitive than wild-type pollen after pollination, 49 although it had an ability to fertilize. Taken together, our results suggest that 50 controlling the nuclear shape in vegetative cells of pollen grains by KAKU4 ensures 51 the orderly migration of the VN and sperm cells in pollen tubes. 52 53

Advancing knowledge of the plant nuclear periphery and its application for crop science

“…Zhou et al [ 33 ] went on to prove that the entire LINC complex was involved. Goto et al [ 43 ] recently show a role for the putative nuclear lamina protein KAKU4 in this process. KAKU4 is highly abundant in VNs and less so in SCNs.…”

“…clustering of telomeres at the INM) with telomere pairing may promote homologous chromosome synapsis, an important step toward recombination events to generate crossovers. Finally, components of the nuclear periphery not only affect meiosis but also fertilization as they are key components in nuclear migration during pollen tube growth as already mentioned in the nuclear movement section [ 42 , 43 ].…”