Expression And Function Analyses Of A Gene Family Encoding A Novel Class Of Proline-rich Proteins In Rice

OsPRP1, a 4–membered gene family in rice (Oryza sativa L), is restricted at least in cereal plants and encodes a novel class of proline-rich proteins (PRP). The 4 OsPRP1s are distinct from the 4 classes of plant PRPs described previously and belong to DUF1210 super family with a single conserved domain.In rice genome, the 4 OsPRP1 genes are tandemly arranged without any interval of other ORFs. Because of the conservatism in coding regions and identical gene structures, they are 4 paralogs from a common progenitor and the divergence time is not long for smaller synonymous substitution rates (KS values returned by PAML analysis). And it is very difficult to distinguish them at RNA or protein level so that the fragments of promoters and partial coding regions were cloned and fused to the 5'-end of a report gene (gus) to detect their expression differences. No GUS signal was detected in transgenic Arabidopsis plants, suggesting their species specificity of expression. And in rice, through GUS staining, the 4 OsPRP1s showed different regimes of expression with functional divergence and overlapping. According to the elements associated with environmental factors, 6 types of plant growth substances and 3 types of abiotic stresses were applied to the transgenic plant lines harboring promoter::gus construct. And the OsPRP1s displayed varied responses to these stimuli, suggesting the functional divergence in gene regulation. Our data revealed that the four paralogs had faced several fates (pseudogenization, subfunctionalization or neofunctionalization) much more complicated than theoretical models suggest. They may play multiple physiological roles during plant growth and development.Plant cell wall is an aqueous network containing diversiform carbohydrates and proteins and play significant roles in many aspects such as protecting and shaping the protoplasts, intercellular communication, cell differentiation, defending...