Polyamines mediate the inhibitory effect of drought stress on nitrogen reallocation and utilization to regulate grain number in wheat.

Drought stress poses a serious threat to grain formation in wheat. Nitrogen (N) plays crucial roles in plant organ development; however, the physiological mechanisms by which drought stress affects plant N availability and mediates the formation of grains in spikes of winter wheat are still unclear. In this study, we determined that pre-reproductive drought stress significantly reduced the number of fertile florets and the number of grains formed. Transcriptome analysis demonstrated that this was related to N metabolism, and in particular, the metabolism pathways of arginine (the main precursor for synthesis of polyamine) and proline. Continuous drought stress restricted plant N accumulation and reallocation rates, and plants preferentially allocated more N to spike development. As the activities of amino acid biosynthesis enzymes and catabolic enzymes were inhibited, more free amino acids accumulated in young spikes. The expression of polyamine synthase genes was down-regulated under drought stress, whilst expression of genes encoding catabolic enzymes was enhanced, resulting in reductions in endogenous spermidine and putrescine. Treatment with exogenous spermidine optimized N allocation in young spikes and leaves, which greatly alleviated the drought-induced reduction in the number of grains per spike. Overall, our results show that pre-reproductive drought stress affects wheat grain numbers by regulating N redistribution and polyamine metabolism.

[Beneficial effects of reciprocating gait orthosis on bladder and bowel functions in paraplegia patients].

OBJECTIVE: To evaluate the beneficial effects of application of a self-designed reciprocating gait orthosis (RGO) combined with comprehensive rehabilitation training on bladder and bowel function in paraplegic patients sustaining spinal cord injuries (SCI). METHODS: Twelve paraplegic patients with complete spinal cord injury at the levels between T(4) and L(1) received the RGO with a comprehensive rehabilitation exercise program carried out before and after fixing. Cold water and colon excretion tests were performed before and 3 months after application of the RGO, and the bladder volume, residue bladder volume, and bladder and bowel pressures were measured in these patients. RESULTS: The 12 paraplegic patients all showed positive results in cold water test before and after RGO application. Before RGO application, 11 of these patients were positive for urine bacteria and only 1 patient was still positive 3 months after the application. The bladder volume and bowel pressure of the patients were significantly increased (P<0.05), while the residue volume and pressure of the bladder were significantly reduced 3 months after RGO application (P<0.05). CONCLUSION: RGO combined with comprehensive rehabilitation training can effectively improve the bladder and bowel function and the quality of life of patients with complete spinal cord injury, suggesting much clinical value for its extensive application.