Characterization of calnexin in soybean roots and hypocotyls under osmotic stress

Calnexin is an endoplasmic reticulum-localized molecular chaperone protein which is involved in folding and quality control of proteins. To evaluate the expression of calnexin in soybean seedlings under osmotic stress, immunoblot analysis was performed using a total membrane protein fraction. Calnexin constantly accumulated at an early growth stage of soybean under normal growth conditions. Expression of this protein decreased in 14-day-old soybean roots when treated with 10% polyethylene glycol for 2 days. Other abiotic stresses such as drought, salinity, cold as well as abscisic acid treatment, similarly reduced accumulation of calnexin and this reduction was correlated with reduction in root length in soybean seedlings under abiotic stresses. When compared between soybean and rice, calnexin expression was not changed in rice under abiotic stresses. Using Flag-tagged calnexin, a 70 kDa heat shock cognate protein was identified as an interacting protein. These results suggest that osmotic or other abiotic stresses highly reduce accumulation of the calnexin protein in developing soybean roots. It is also suggested that calnexin interacts with a 70 kDa heat shock cognate protein and probably functions as molecular chaperone in soybean.     

一个特异水稻原纤蛋白FBN11的生物信息学和基因表达特性分析

Fibrillin 11(FBN 11)是植物质体中FBN蛋白家族的重要成员之一,比其他成员多300~500个氨基酸残基,说明其可能存在某些特异性结构和功能。本研究在水稻幼苗中扩增获得到了一个受非生物逆境胁迫诱导的OsFBN11基因的全长cDNA,该基因含有12个内含子和13个外显子。其编码蛋白的分子量为72.36 kD,pI值为9.26。生物信息学分析结果表明,该蛋白含有无规则卷曲、α螺旋和β-折叠3种氨基酸二级结构,不含有跨膜结构域,蛋白亲水性强,PSORT软件预测该蛋白可能定位于叶绿体中。进一步对14种植物FBN11蛋白的同源性和5个物种该蛋白的保守结构域分析,发现该蛋白兼有典型的PAP-Fibrillin结构域和蛋白激酶PKc结构域。水稻全生育期芯片分析显示该基因主要在愈伤组织、叶片和根系中高水平表达。RT-PCR检测结果显示,该基因在水稻幼苗中受ABA、NaCl和干旱胁迫处理上调表达。上述结果表明,OsFBN11可能在水稻质体发育和抗非生物胁迫反应中发挥重要作用。     

Piriformospora indica?rescues growth diminution of rice seedlings during high salt stress

Piriformospora indica association has been reported to increase biotic as well as abiotic stress tolerance of its host plants. We analyzed the beneficial effect of P. indica association on rice seedlings during high salt stress conditions (200 and 300 mM NaCl). The growth parameters of rice seedlings such as root and shoot lengths or fresh and dry weights were found to be enhanced in P. indica-inoculated rice seedlings as compared with non-inoculated control seedlings, irrespective of whether they are exposed to salt stress or not. However, salt-stressed seedlings performed much better in the presence of the fungus compared with non-inoculated control seedlings. The photosynthetic pigment content [chlorophyll (Chl) a, Chl b, and carotenoids] was significantly higher in P. indica-inoculated rice seedlings under high salt stress conditions as compared with salt-treated non-inoculated rice seedlings, in which these pigments were found to be decreased. Proline accumulation was also observed during P. indica colonization, which may help the inoculated plants to become salt tolerant. Taken together, P. indica rescues growth diminution of rice seedlings under salt stress.