Analysis of Poly(ADP-Ribose) Polymerases in Arabidopsis Telomere Biology

Abstract

Maintaining the length of the telomere tract at chromosome ends is a complex process vital to normal cell division. Telomere length is controlled through the action of telomerase as well as a cadre of telomere-associated proteins that facilitate replication of the chromosome end and protect it from eliciting a DNA damage response. In vertebrates, multiple poly(ADP-ribose) polymerases (PARPs) have been implicated in the regulation of telomere length, telomerase activity and chromosome end protection. Here we investigate the role of PARPs in plant telomere biology. We analyzed Arabidopsis thaliana mutants null for PARP1 and PARP2 as well as plants treated with the PARP competitive inhibitor 3-AB. Plants deficient in PARP were hypersensitive to genotoxic stress, and expression of PARP1 and PARP2 mRNA was elevated in response to MMS or zeocin treatment or by the loss of telomerase. Additionally, PARP1 mRNA was induced in parp2 mutants, and conversely, PARP2 mRNA was induced in parp1 mutants. PARP3 mRNA, by contrast, was elevated in both parp1 and parp2 mutants, but not in seedlings treated with 3-AB or zeocin. PARP mutants and 3-AB treated plants displayed robust telomerase activity, no significant changes in telomere length, and no end-to-end chromosome fusions. Although there remains a possibility that PARPs play a role in Arabidopsis telomere biology, these findings argue that the contribution is a minor one.

Protein Poly(ADP-ribosyl)ation Regulates Arabidopsis Immune Gene Expression and Defense Responses

“…However, Arabidopsis atparp1/2 double mutant is largely morphologically similar with WT plants and does not display any obvious growth defects. Although Arabidopsis atparp1/2 double mutant was hypersensitive to genotoxic stress, they did not have significant changes in telomere length nor end-to-end chromosome fusions [30] . Albeit mainly expressed in developing seeds, AtPARP3 may have redundant functions with AtPARP1 and AtPARP2 in maintaining genome stability.…”

“…We tested the involvement of AtPARPs in plant innate immunity and immune gene activation. Because of the potential functional redundancy of AtPARP1 and AtPARP2 [30] , [31] , we performed disease assay and analyzed defense gene expression in atparp1atparp2 ( atparp1/2 ) double mutant. The atparp1/2 mutant plants were more susceptible to virulent P. syringae pv.…”

Agrobacterium T‐DNA integration into the plant genome can occur without the activity of key non‐homologous end‐joining proteins

“…Bleomycin sensitivity assay was done as described earlier (Vaghchhipawala et al ., ). The Arabidopsis genes and ecotypes investigated, and the corresponding mutants, are: KU70 [At1g16970; Col‐0: SALK_123114 (Heacock et al ., ; Kannan et al ., ; Qi et al ., )]; KU80 (At1g48050; Col‐0: SAIL_714_A04; Ws: FLAG_396B06); ATM [At3g48190; Col‐0: SALK_006953 (Vespa et al ., )]; ATR [At5g40820; Col‐0: SALK_032841 (Vespa et al ., )]; LIG4 [At5g57160; Col‐0: SALK_044027 ( Atlig4‐2 ); Col‐0: SAIL_597_D10 ( Atlig4‐5 , Waterworth et al ., )]; LIG6 [At1g66730; Col‐0: SALK_079499‐1 ( Atlig6‐1 , Waterworth et al ., ); Ws: FLAG_437H07 ( Atlig6‐2 , Waterworth et al ., )]; XRCC1 (At1g80420; Col‐0: SALK_125373); PARP1 [At4g02390; Col‐0: SALK_140400 (Boltz et al ., )]. N .…”

The DNA translocase RAD5A acts independently of the other main DNA repair pathways, and requires both its ATPase and RING domain for activity in Arabidopsis thaliana

“…PARPs catalyze the synthesis and transfer of poly ADP‐ribose (PAR) to target proteins, and the mammalian ortholog of AtPARP1 is a prominent factor in SSB repair and BER (reviewed in Gibson and Kraus, ). At parp1 mutants are sensitive towards MMS, indicating a likely conservation of function among animals and plants (Boltz et al ., ). We were able to reproduce the sensitivity of parp1‐1 towards MMS‐induced DNA damage, whereas we could not detect any hypersensitivity against the CL‐inducing agents MMC or cisplatin.…”

“…The functions of the PARP1 ortholog in Arabidopsis include a role within stress tolerance, programmed cell death and backup non‐homologous end joining (B‐NHEJ) (Amor et al ., ; de Block et al ., ; Vanderauwera et al ., ; Jia et al ., ). Furthermore, PARP1 seems to be involved in the repair of base alterations, with a parp1 mutant displaying increased sensitivity towards MMS‐induced DNA damage (Boltz et al ., ).…”