Immunological evidence for accumulation of two high-molecular-weight (104 and 90 kDa) HSPs in response to different stresses in rice and in response to high temperature stress in diverse plant genera

Rice seedlings accumulate stainable amounts of the 104 and 90 kDa polypeptides in response to high temperature stress. We have purified and raised highly specific polyclonal antisera against both of these polypeptides. In western blotting experiments, we find that these proteins are accumulated to different extents in rice seedlings subjected to salinity (NaCl), water stress, low-temperature stress and exogenous abscisic acid application. These proteins also accumulated when rice seedlings grown in pots under natural conditions were subjected to water stress by withholding watering. Seedlings of Triticum aestivum, Sorghum bicolor, Pisum sativum, Zea mays, Brassica juncea and mycelium of Neurospora crassa showed accumulation of the immunological homologues of both the 104 and the 90 kDa polypeptides, in response to high-temperature stress. We have earlier shown that shoots of rice seedlings exposed to heat shock accumulate a 110 kDa polypeptide which is an immunological homologue of the yeast HSP 104 (Singla and Grover, Plant Mol Biol 22: 1177–1180, 1993). Employing anti-rice HSP 104 antibodies and anti-yeast HSP 104 antibodies together, we provide evidence that rice HSP 104 is different from the earlier characterized rice HSP 110.     

Rheology and composition of a multi-utility exopolymer from a desert borne cyanobacterium Anabaena variabilis

The desert cyanobacterium Anabaena variabilis produces an exopolymer during the stationary growth phase in batch culture. Optimal polymer production was observed at pH?10 under phosphorus limitation. Chemical analysis showed it to be composed of 49% carbohydrate and 19% protein. Monosaccharide analysis revealed a heteropolysaccharidic nature with glucose, mannose, and galactose as the main neutral sugars. Infrared (IR) spectrum of the exopolymer showed absorption bands at 1,645 and 1,421?cm^?1 characteristic of C=O in the carboxylate group. Strong band was observed at 1,072?cm^?1 due to C–O–C or C–O–P stretching vibrations. A band at 2,363?cm^?1 corresponding to C–H stretch of protein was also observed. IR spectrum suggested that the exopolymer is nonsulfated. Rheological properties of the polymer showed marked shear thinning non-Newtonian behavior in the concentration range of 0.1–0.4%. However, it appeared to undergo change in the internal structure on shearing thereby exhibiting thixotropic behavior. The polymer possessed 75% flocculating ability vis a vis alum, 71% emulsification of hexadecane, and good thermal stability making it a potent candidate for multiple industrial applications. The exopolymer bound 156?g H₂O g^?1 and exhibited antibacterial activity against Staphylococcus aureus suggesting a potential for application in wound management as well.