In flowering plants, the male gametophyte (pollen) delivers the male gametes (sperm nuclei) to the embryo sac for double fertilization. Interactions between WRKY proteins and VQ motif-containing proteins are required to control these complicated transcriptional networks. However, the downstream target genes and mechanisms underlying the WRKY2/34–VQ20 mediated processes are still not fully understood.
In a newly study published in Frontiers in Plant Science, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) reported that WRKY2 and WKRY34 repressed the expression of MYB97, MYB101, and MYB120 during male gametogenesis. MYB expression was up-regulated in the w2-1 w34-1 vq20-1 triple mutant relative to the wild-type during male gametogenesis.
They found that MYBs are expressed in tricellular pollen and their expression peaks in mature pollen, while transcripts of WRKY34 and VQ20 decreased gradually during male gametogenesis and were lowest in mature pollen. The expression levels of MYB97 and MYB120 were highest in the w2-1 w34-1 vq20-1 triple mutant plants, followed by the w2-1 w34-1 double mutants.
They further found that the expression levels of MYBs were not properly regulated during male gametogenesis in the w2-1 w34-1 vq20-1 triple mutant plants. When MYB97 expression was up-regulated in a wild-type background, the MYB97-overexpression lines had a similar phenotype as the w2-1 w34-1 vq20-1 triple mutant, with defects in pollen viability, pollen germination, and pollen tube length.
The study indicated that WRKY2/34–VQ20 complexes control the expression levels of MYBs during male gametogenesis in plants. The uncontrolled regulation of transcriptional factors may affect pollen development in Arabidopsis.
YU Diqiu, Ph.D Principal Investigator
Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China
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