SIMYB1 and SIMYB2, two new MYB genes from tomato, transcriptionally regulate cellulose biosynthesis in tobacco

Cellulose, a major constituent of plant biomass, is synthesized by a cellulose synthase complex. It has been demonstrated that MYB genes transcriptionally regulate cellulose synthase in Arabidopsis. However, little is known about this process in tomato. Here, two MYB （SIMYB1/2） and three cellulose synthase （CESA） （SICESA41516） genes were isolated. SIMYB1/2 and SICESA4/5/6 accumulation was found to correspond to cellulose accumulation in different tissues of tomato. Dual luciferase assays indicated that these two MYBs were transcriptional activators that interact with promoters of SICESA4/5/6. Moreover, SIMYB2 could also activate promoters of SIMYB1/2, suggesting the possible underlying auto-activation mech- anisms for MYB transcription factors. Transient over-expression of SlMYB1/2 in Nicotiana tabacum up-regulated tobacco endogenous NtCESA genes and increased cellulose accumulation. The function of SIMYB112 was further investigated using stable transformation and the results indicated that N. tabacum lines heterologous expressing SIMYB1/2 displayed a pleiotropic phenotype, long and narrow leaves, with NtCESA induced and significant increase of cellulose. In conclusion, our data suggest that tomato SIMYB1/2 have transcriptional regulatory roles in cellulose biosynthesis and SIMYB2 was more effective than SIMYB1, which may due to the transcriptional activation by SIMYB2 on SIMYB1 and itself.

miR-300-3p通过调控细胞自噬减轻缺氧/复氧诱导H9c2心肌细胞损伤的研究

目的探究miR-300-3p对缺氧/复氧(H/R)诱导H9c2大鼠心肌细胞损伤的影响及其机制。方法将H9c2细胞分成对照组、miR-NC组和miR-300-3p组,miR-NC组转染miR-NC阴性对照,miR-300-3p组转染miR-300-3p模拟物(mimics)以过表达miR-300-3p。对照组于正常条件下培养,miR-NC组和miR-300-3p组在转染24 h后进行缺氧24 h/复氧6 h的处理。用细胞计数试剂法检测心肌细胞活力,用乳酸脱氢酶(LDH)测定细胞活性,用流式细胞术检测细胞凋亡情况,用蛋白质印迹法检测B淋巴细胞瘤-2蛋白(Bcl-2)、Bcl-2相关X蛋白(Bax)、选择性自噬接头蛋白(P62)、Bcl-2同源结构域蛋白(Beclin-1)和微管相关蛋白1A/1B-轻链3(LC3)的表达水平。结果H/R处理后,miR-300-3p组、miR-NC组和对照组的细胞活力分别为(52.21±3.77)%,(34.27±3.21)%和100.00%,LDH相对释放量分别为1.92±0.25,3.05±0.37和1.00,细胞凋亡率分别为(26.10±3.70)%,(37.10±7.70)%和(4.70±0.90)%,Bcl-2蛋白相对表达水平分别为0.66±0.07,0.34±0.10和1.00,Bax蛋白相对表达水平分别为0.43±0.07,1.47±0.12和1.00,P62蛋白相对表达水平分别为1.14±0.20,2.20±0.23和1.00,Beclin-1蛋白相对表达水平分别为2.55±0.28,0.66±0.12和1.00,LC3蛋白相对表达水平分别为3.12±0.37,0.73±0.10和1.00。miR-300-3p组的上述指标与miR-NC组相比,差异均有统计学意义(均P<0.05)。miR-NC组的上述指标与对照组比较,差异均有统计学意义(均P<0.05)。结论过表达miR-300-3p可以抑制H/R诱导的H9c2心肌细胞损伤,其机制可能与激活细胞自噬有关。