SD-RLK28 positively regulates pollen hydration on stigmas as a PCP-Bß receptor in Arabidopsis thaliana.

Pollen hydration on dry stigmas is strictly regulated by pollen-stigma interactions in Brassicaceae. Although several related molecular events have been described, the molecular mechanism underlying pollen hydration remains elusive. Multiple B-class pollen coat proteins (PCP-Bs) are involved in pollen hydration. Here, by analyzing the interactions of two PCP-Bs with three Arabidopsis thaliana stigmas strongly expressing S-domain receptor kinase (SD-RLK), we determined that SD-RLK28 directly interacts with PCP-Bß. We investigated pollen hydration, pollen germination, pollen tube growth, and stigma receptivity in the sd-rlk28 and pcp-bß mutants. PCP-Bß acts in the pollen to regulate pollen hydration on stigmas. Loss of SD-RLK28 had no effect on pollen viability, and sd-rlk28 plants had normal life cycles without obvious defects. However, pollen hydration on sd-rlk28 stigmas was impaired and pollen tube growth in sd-rlk28 pistils was delayed. The defect in pollen hydration on sd-rlk28 stigmas was independent of changes in reactive oxygen species levels in stigmas. These results indicate that SD-RLK28 functions in the stigma as a PCP-Bß receptor to positively regulate pollen hydration on dry stigmas.

Genome-wide identification of the valine-glutamine motif containing gene family and the role of VQ25-1 in pollen germination in Brassica oleracea.

BACKGROUND: The plant-specific valine-glutamine (VQ) motif containing proteins tightly regulate plant growth, development, and stress responses. However, the genome-wide identification and functional analysis of Brassica oleracea (B. oleracea) VQ genes have not been reported. OBJECTIVE: To identify the VQ gene family in B. oleracea and analyze the function of Bo25-1 in pollen germination. METHODS: The Hidden Markov Model (HMM) of VQ family was used to query the BoVQ genes in the B. oleracea genome. The BoVQ genes preferentially expressed in anthers were screened by qRT-PCR. Subcellular localization of VQ25-1 was observed in Nicotiana benthamiana (N. benthamiana) leaves. To analysis the role of BoVQ25-1 in pollen germination, the expression of BoVQ25-1 was suppressed using antisense-oligonucleotides (AS-ODN). RESULTS: A total of 64 BoVQ genes were identified in the B. oleracea genome. BoVQ25-1 was found to be preferentially expressed in the B. oleracea anthers. BoVQ25-1 was cloned from the anthers of the B. oleracea cultivar 'Fast Cycle'. BoVQ25-1 is localized to the nucleus. The pollen germination rate significantly decreased after AS-ODN treatment. CONCLUSION: Sixty-four BoVQ genes were identified in the B. oleracea genome, of which BoVQ25-1 plays an important role in pollen germination.