ABSTRACT
Polyphenol oxidase (PPO) activity in sugarcane (a C4 grass) was highest in the growing point and declined down the stalk. Sugarcane PPO with an apparent molecular mass of 45 kDa was purified to homogeneity from immature stem tissue. Western analysis of sugarcane extracts with a polyclonal antibody raised to this protein suggested it resulted from cleavage of a 60 kDa protein during purification. The antibody was used to screen a sugarcane stem cDNA library. A full-length PPO clone (sugppo 1) was characterised and shown to encode a 67 kDa precursor protein comprising a plastid transit sequence of 8 kDa and a mature PPO protein of 59 kDa. High levels of expression of sugppo 1 were detected in the growing point of the stalk and in the immature tissue immediately below it, but no message was detected in RNA from mature stem or leaf. Comparison with other PPO sequences indicated that sugppo 1 was significantly different to PPO genes in C3 dicotyledonous plants.
Subject(s)
Catechol Oxidase/genetics , DNA, Complementary , Poaceae/genetics , Amino Acid Sequence , Catechol Oxidase/isolation & purification , Gene Library , Molecular Sequence Data , Plant Shoots/chemistry , Plastids , Poaceae/classification , Poaceae/enzymology , Protein Precursors/genetics , Protein Sorting Signals/genetics , RNA, Plant/analysis , Sequence Analysis, DNA , Sequence Homology, Amino AcidABSTRACT
Seasonal Affective Disorder (SAD) has been characterised by two or more depressive episodes in autumn or winter (with remission the following spring or summer), decreased energy, increased sleep, increased appetite, weight gain and carbohydrate craving. SAD patients were identified in a Swiss-German population; 22 participated in a light-therapy protocol (1 week bright white light 2,500 lux or dim yellow light 250 lux, from 06-08 h and 18-20 h). Both observer and self-ratings indicated a significant diminution of depressive symptoms with both lights. One week after withdrawal from yellow light, depression ratings relapsed to previous values; remission lasted longer after bright white light. Global VAS self-rating scales for "mood" and "well-being" however, and the Hamilton scale for atypical SAD symptoms, differentiated clearly between bright and dim light: only bright light showed an improvement that persisted after withdrawal. These results suggest that even though a placebo effect cannot be excluded, 4 h explicit light exposure/day may not be a negligible quantity. Light treatment promises to be a useful non-pharmacological intervention in certain forms of depressive illness.
