UV-B-induced DNA damage mediates expression changes of cell cycle regulatory genes in Arabidopsis root tips

Abstract

Even though a number of studies have shown that UV-B radiation inhibits plant growth and regulates the cell cycle progress, little is known about the molecular and cellular mechanisms. Here, we developed a synchronous root-tip cell system to investigate expression changes of cell cycle marker genes and DNA damage under UV-B radiation. Expression analysis of cell cycle marker genes revealed that G1-to-S transition in root-tip cells was accomplished within 6 h. In the in vivo synchronous root-tip cells, high level of UV-B radiation (0.45 W m(-2)) induced expression changes of the cell cycle regulatory genes. Genes involved in G1-to-S transition, Histone H4 and E2Fa, were down-regulated by UV-B radiation during 2-6 h; whereas transcripts for KRP2, a negative regulator of G1-to-S transition, were up-regulated by UV-B at 2 h. The peak time for transcript level of CYCD3;1, a positive factor in G1-to-S transition, was delayed by UV-B radiation. Interestingly, a medium level of UV-B radiation (0.25 W m(-2)) did not change the expression of these genes in root tip cells from wild type. However, cell cycle regulatory genes were greatly affected in uvh1 mutant, which exhibited higher content of cyclobutane pyrimidine dimers (CPDs). Ascorbic acid treatment did not change the expression pattern of cell cycle regulatory genes that were affected by high-level UV-B. Our results implied that UV-B-induced DNA damage results in the delay of G1-to-S transition of plant cell cycle. UV-B-induced G1-to-S arrest may be a protective mechanism that prevents cells with damaged DNA from dividing and may explain the plant growth inhibition under increased solar UV-B radiation.

Repression of Growth Regulating Factors by the MicroRNA396 Inhibits Cell Proliferation by UV-B Radiation in Arabidopsis Leaves

“…Different letters indicate statistically significant differences applying ANOVA test (P < 0.05). radiation were analyzed using actively dividing cells of Arabidopsis root tips (Jiang et al, 2011a). High levels of UV-B radiation induced expression changes of the cell cycle regulatory and DNA damage genes, suggesting that UV-B-induced DNA damage results in the delay of the G1-to-S transition of the cell cycle and that UV-B-induced G1-to-S arrest may be a protective mechanism that prevents cells with damaged DNA from dividing.…”

Molecular cloning and characterization of a proliferating cell nuclear antigen gene by chemically induced male sterility in wheat (Triticum aestivum L.)

“…In our semi-quantitative RT-PCR assay, we found that Histone H4 expression was lower in 1376-CMIS than in 1376, indicating that cell-cycle arrest induced by SQ-1 in 1376 anthers was a consequence of DNA damage, and this regulation might be a response to DNA damage. In Arabidopsis, Histone H4 is downregulated by UV-B radiation, suggesting that UV-B-induced DNA damage results in a delay of the G1-to-S transition in plant cell cycles (Jiang et al, 2011). In addition, TaPCNA expression was higher in 1376-CMIS than in 1376 at all three stages.…”

UV-B induced morphogenesis

“…Summary of morphogenic processes in uV-B exposed plants. uV-B can directly inhibit growth through cellular damage (Jiang et al, 2011). 27 alternatively, dwarfism is mediated through the uVr8 pathway (Favory et al, 2009) 18 , or uVr8 compensates for inhibitory effects of uV-B on growth (Wargent et al, 2009b).…”

“…uV-B can directly inhibit growth through cellular damage (Jiang et al, 2011). 27 alternatively, dwarfism is mediated through the uVr8 pathway (Favory et al, 2009) 18 , or uVr8 compensates for inhibitory effects of uV-B on growth (Wargent et al, 2009b). 8 the uVr8 pathway may directly regulate morphogenesis, or this may involve crosstalk with other processes, including flavonoid accumulation, endoreduplication and antioxidant scavenging.…”

“…25 Endoreduplication is a determinant of cell size, with higher ploidy levels associated with bigger cells. 26 UV-B impedes cell cycle progression, 27 decreasing both cell numbers and endoreduplication. 26 However, UV-B also downregulates the transcription factor E2Fe/DEL1, which represses onset of endoreduplication, and expression of DNA photolyase PHR1.…”