Mixed cropping has the potential to enhance flood tolerance of drought-adapted grain crops.

Recently, the occurrences of extreme flooding and drought, often in the same areas, have increased due to climate change. Wetland plant species are known to oxygenate their rhizospheres by releasing oxygen (O2) from their roots. We tested the hypothesis that wetland species could help upland species under flood conditions; that is, O2 released from the wetland crop roots would ameliorate rhizosphere O2-deficient stress and hence facilitate upland crop root function. Flooding tolerance of upland-adapted staple crops-pearl millet (Pennisetum glaucum) and sorghum (Sorghum bicolor) mix-cropped with rice (Oryza spp.) was investigated in glasshouse and laboratory. We found a phenomenon that strengthens the flood tolerance of upland crops when two species-one wetland and one drought tolerant-were grown using the mixed cropping technique that results in close tangling of their root systems. This technique improved the photosynthetic and transpiration rates of upland crops subjected to flood stress (O2-deficient nutrient culture). Shoot relative growth rates during the flooding period (24 days) tended to be higher under mixed cropping compared with single cropping. Radial oxygen loss from the wetland crop roots might be contributed to the phenomenon observed. Mixed cropping of wet and dryland crops is a new concept that has the potential to overcome flood stress under variable environmental conditions.

A novel glycerophosphodiester phosphodiesterase, GDE5, controls skeletal muscle development via a non-enzymatic mechanism.

Mammalian glycerophosphodiester phosphodiesterases (GP-PDEs) have been identified recently and shown to be implicated in several physiological functions. This study isolated a novel GP-PDE, GDE5, and showed that GDE5 selectively hydrolyzes glycerophosphocholine (GroPCho) and controls skeletal muscle development. We show that GDE5 expression was reduced in atrophied skeletal muscles in mice and that decreasing GDE5 abundance promoted myoblastic differentiation, suggesting that decreased GDE5 expression has a counter-regulatory effect on the progression of skeletal muscle atrophy. Forced expression of full-length GDE5 in cultured myoblasts suppressed myogenic differentiation. Unexpectedly, a truncated GDE5 construct (GDE5DeltaC471), which contained a GP-PDE sequence identified in other GP-PDEs but lacked GroPCho phosphodiesterase activity, showed a similar inhibitory effect. Furthermore, transgenic mice specifically expressing GDE5DeltaC471 in skeletal muscle showed less skeletal muscle mass, especially type II fiber-rich muscle. These results indicate that GDE5 negatively regulates skeletal muscle development even without GroPCho phosphodiesterase activity, providing novel insight into the biological significance of mammalian GP-PDE function in a non-enzymatic mechanism.

Involvement of membrane protein GDE2 in retinoic acid-induced neurite formation in Neuro2A cells.

We show that a glycerophosphodiester phosphodiesterase homolog, GDE2, is widely expressed in brain tissues including primary neurons, and that the expression of GDE2 in neuroblastoma Neuro2A cells is significantly upregulated during neuronal differentiation by retinoic acid (RA) treatment. Stable expression of GDE2 resulted in neurite formation in the absence of RA, and GDE2 accumulated at the regions of perinuclear and growth cones in Neuro2A cells. Furthermore, a loss-of-function of GDE2 in Neuro2A cells by RNAi blocked RA-induced neurite formation. These results demonstrate that GDE2 expression during neuronal differentiation plays an important role for growing neurites.

Isolation and characterization of two serpentine membrane proteins containing glycerophosphodiester phosphodiesterase, GDE2 and GDE6.

Serpentine membrane protein with a glycerophosphodiester phosphodiesterase (GP-PDE) motif, GDE3, is involved in morphological change of cells and accelerates the program of osteoblast differentiation, suggesting that mammalian GP-PDEs play an important role in the regulation of cytoskeletal modification. Here, we isolated two cDNAs encoding serpentine membrane proteins, GDE2 and GDE6, containing GP-PDE motif from mouse cDNA libraries. The deduced sequence of GDE2 contains 607 amino acids with seven putative transmembrane regions. GDE6 was composed of 633 amino acids also with seven putative transmembrane regions. In amino acid sequences, GDE2 and GDE6 are 43.7% and 34.3% identical to GDE3, respectively. Although GDE3 mRNA is highly expressed in bone tissue and spleen, GDE2 mRNA was expressed in a variety of mouse tissues including lung and heart, while the GDE6 transcript was particularly abundant in spermatocytes of mouse testis. Immunohistochemical analyses using anti-GDE2 antibody showed that GDE2 protein is expressed in the epithelial cell layer of mouse lung. These results suggest that GP-PDEs are differentially expressed in mouse tissues, and might have distinct roles.