Protein differential expression in the elongating cotton (Gossypium hirsutum L.) fiber under nitrogen stress

Nitrogen (N) is an essential macronutrient and an important factor limiting agricultural productivity. N deficient or excess conditions often occur during the cotton growth season and incorrect N application may affect cotton fiber yield and quality. Here, the influence of N stress on the cotton fiber proteome was investigated by two-dimensional gel electrophoresis and mass spectrometry. The results indicated that N application rate affects nitrogen accumulation in fiber cells and fiber length. The proteins differentially expressed during N stress were mainly related to plant carbohydrate metabolism, cell wall component synthesis and transportation, protein/amino acid metabolism, antioxidation and hormone metabolism. The most abundant proteins were C metabolism-related. Ten days post anthesis is a critical time for fiber cells to perceive environmental stress and most proteins were suppressed in both N deficient and N excess conditions at this sampling stage. However, several N metabolism proteins were increased to enhance N stress tolerance. Excess N may suppress carbohydrate/energy metabolism in early fiber development much like N deficiency. These results have identified some interesting proteins that can be further analyzed to elucidate the molecular mechanisms of N tolerance.