MdMYB44-like positively regulates salt and drought tolerance via the MdPYL8-MdPP2CA module in apple.

Abscisic acid (ABA) is involved in salt and drought stress responses, but the underlying molecular mechanism remains unclear. Here, we demonstrated that the overexpression of MdMYB44-like, an R2R3-MYB transcription factor, significantly increases the salt and drought tolerance of transgenic apples and Arabidopsis. MdMYB44-like inhibits the transcription of MdPP2CA, which encodes a type 2C protein phosphatase that acts as a negative regulator in the ABA response, thereby enhancing ABA signaling-mediated salt and drought tolerance. Furthermore, we found that MdMYB44-like and MdPYL8, an ABA receptor, form a protein complex that further enhances the transcriptional inhibition of the MdPP2CA promoter by MdMYB44-like. Significantly, we discovered that MdPP2CA can interfere with the physical association between MdMYB44-like and MdPYL8 in the presence of ABA, partially blocking the inhibitory effect of the MdMYB44-like-MdPYL8 complex on the MdPP2CA promoter. Thus, MdMYB44-like, MdPYL8, and MdPP2CA form a regulatory loop that tightly modulates ABA signaling homeostasis under salt and drought stress. Our data reveal that MdMYB44-like precisely modulates ABA-mediated salt and drought tolerance in apples through the MdPYL8-MdPP2CA module.

[Influence of calcineurin on apoptosis of pre-B lymphocytes and the leukemia cells derived from pre-B lymphocytes].

This study was aimed to compare the differential expressions of calcineurin (PP2B, PP3) in the mouse Pre-B cell lines (S9) and the tumor cell lines (S4C2) derived from pre-B lymphocytes, and to clarify its possible mechanism involving in the leukemia cell apoptosis. The quantitative real-time PCR was used to detect the differential expressions of H2AX-associated phosphakinase ATM, ATR, DNA-PKs, JNK1, P38 and the γ-H2AX-related phosphatase PP1, PP2A, calcineurin, PP4, PP6, PP5 between S9 and S4C2 cell lines. CCK-8 assay and flow cytometry were used to detect the effect of imatinib (IM) and cyclosporine A (CsA) on cytotoxicity and apoptosis of 2 cell lines. The Western blot was used to detect the effects of 2 drugs on apoptosis of S9 and S4C2 cell lines. The results showed that the expression level of calcineurin gene in the leukemia cell S4C2 was about 3.5 times of that in S9 cells, while the expression of other genes in these 2 kinds of cells was not significantly different. The apoptosis and toxicity of IM and CsA on S4C2 cells was significantly stronger than that on S9 cells. The expression level of calcineurin in S4C2 cells was higher than that in S9 cells.When CsA inhibited the calcineurin activity, the expression of DNA damage marker γ-H2AX in S9 cells was significantly lower than that in S4C2 cells,while the expression level of γ-H2AX between the two cell lines was no significantly different after treatment with imatinib, the expression level of γ-H2AX in S9 cells was lower than that in S4C2 cells when the two drugs were combined. It is concluded that the calcineurin plays a role of anti-apoptosis in B leukemic cells, cyclosporine A can promote the leukemia cell apoptosis.

[Treatment of leukemia with immunized donor cell infusion after nonmyeloablative haploidentical bone marrow transplantation].

This study was purposed to investigate the therapeutic effects of early transfusion of immunized donor lymphocytes after haploidentical transplantation by means of mouse model of nonmyeloablative haploidentical bone marrow transplantation. CB6F1 female mouse was served as recipient and C57BL/6 male mouse was served as donor. Each CB6F1 female mouse was subjected to intravenous transfusion with 1×10(6) erythroleukemia (EL9611) cells at day 4 before transplantation, followed with intraperitoneal injection of Ara-C (0.015 g) respectively at day 2 and day 1, then conditioned for BMT with TBI (450 cGy) at day 1 before transplantation. After conditioning (day 0), each of recipients was transplanted with 6×10(7) mixture of bone marrow and spleen cells from the C57BL/6 mice, and was infused with 6 × 10(7) immunized donor lymphocytes at day 15 after transplantation. All treated animals were evaluated for survival, development of leukemia and aGVHD. The donor CD3(+) cell chimerism and sex determining region Y gene (SRY)in recipients were monitored periodically after transplantation. The results showed tht all mice with only inoculation of 10(6) EL9611 cells survived for 15 ± 1 days (n = 4); all mice of other groups obtained the varying degrees of implantation. SRY could be detected at day 30 and 60 after transplantation. The chimerism of donor CD3(+) cells in mixed bone marrow transplantation (MT) group at day 14, 30 and 60 respectively reached 17.95% ± 12.03%, 37.34% ± 2.78% and 47.06% ± 6.1%. In donor lymphocyte infusion (DLI) group it reached 69.78% ± 12.62%, 75% ± 15.97%, 83.41% ± 16.07% at day 30, 45 and 60 after transplantation. The mice of MT and DLI group survived for 66.66 ± 1.47 days and 78.2 ± 7.82 days. It is concluded that the high tumor burden before transplantation can affect donor cell engraftment and prognosis.Early post-transplanted infusion of immunized lymphocytes from donor can help to improve the therapeutic efficacy and survival.