J Integr Plant Biol ›› 2012, Vol. 54 ›› Issue (7): 456-470.DOI: 10.1111/j.1744-7909.2012.01134.x

Special Issue: Cell Biology and Functions

• Cell and Developmental Biology • Previous Articles     Next Articles

The Ca2+-dependent DNases are Involved in Secondary Xylem Development in Eucommia ulmoides

Hui-Min Chen1, Yu Pang1, Jun Zeng1, Qi Ding1, Shen-Yi Yin1, Chao Liu1, Meng-Zhu Lu2, Ke-Ming Cui1 and Xin-Qiang He1*   

  1. 1State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China
    2Laboratory of Biotechnology, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China
  • Received:2011-12-24 Accepted:2012-06-05 Published:2012-06-13
  • About author:*Corresponding author Tel: +86-10-62757016, Fax: +86-10-62751526; Email: hexq@pku.edu.cn

Abstract:

Secondary xylem development has long been recognized as a typical case of programmed cell death (PCD) in plants. During PCD, the degradation of genomic DNA is catalyzed by endonucleases. However, to date, no endonuclease has been shown to participate in secondary xylem development. Two novel Ca2+-dependent DNase genes, EuCaN1 and EuCaN2, were identified from the differentiating secondary xylem of the tree Eucommia ulmoides Oliv., their functions were studied by DNase activity assay, in situ hybridization, protein immunolocalization and virus-induced gene silencing experiments. Full-length cDNAs of EuCaN1 and EuCaN2 contained an open reading frame of 987 bp, encoding two proteins of 328 amino acids with SNase-like functional domains. The genomic DNA sequence for EuCaN1 had no introns, while EuCaN2 had 8 introns. EuCaN1 and EuCaN2 digested ssDNA and dsDNA with Ca2+-dependence at neutral pH. Their expression was confined to differentiating secondary xylem cells and the proteins were localized in the nucleus. Their activity dynamics was closely correlated with secondary xylem development. Secondary xylem cell differentiation is influenced by RNAi of endonuclease genes. The results provide evidence that the Ca2+-dependent DNases are involved in secondary xylem development.

Key words: Ca2+-dependent DNase, programmed cell death, secondary xylem development, secondary wall formation, Eucommia ulmoides

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