The sequencing of the Arabidopsis genome and the generation of multiple EST libraries has provided the scientific community with a huge amount of sequence information and has spurred the development of methods that can use this information to ascertain gene function. One such approach, undertaken in our laboratory, involved over-expressing or down-regulating 89 different ESTs under the control of the 35S promoter and scouring the transgenic plants produced for growth abnormalities. The plentiful phenotype is the result of the over-expression of AT2G47270 and was one of the six abnormal phenotypes produced by the above approach.
The plentiful phenotype is pleiotropic and has similarities to a large number of characterised mutants with shorter hypocotyls and roots, smaller, rounder rosette leaves and shorter inflorescences with reduced apical dominance. The shorter hypocotyls and roots of plentiful are due to a decrease in cell elongation and visual inspection of stem epidermal cells suggest that cell elongation is also reduced in plentiful inflorescences. Although our results suggest that cell expansion is reduced in plentiful rosette leaves, further evidence is required to determine whether cell elongation, cell division or both is reduced in plentiful. Down-regulation of the PLENTIFUL gene was attempted using an RNAi approach but none of the transgenic lines showed a decrease in PLENTIFUL mRNA levels.
Among the mutants with similarities to plentiful are those that have altered synthesis, sensitivity or response to the plant hormones auxin, ethylene, gibberellins, abscisic acid and brassinosteroids. The response of plentiful to IAA, the auxin transport inhibitor NPA, ethylene, the ethylene biosynthesis inhibitor AVG, gibberellin, the gibberellin biosynthesis inhibitor paclobutrazol and abscisic acid were assayed. Results suggest that plentiful has a decreased response to auxin, ethylene, gibberellin and abscisic acid. Time constraints dictated that experiments assaying plentiful’s response to brassinosteroids could not be performed.
The expression pattern of a gene provides clues to its function. To this end, the expression pattern of PLENTIFUL was examined using a promoter-GUS fusion. The expression pattern of PLENTIFUL suggests a role in plant senescence. PLENTIFUL is expressed in aging rosette leaves, floral organs increasing with flower age, in the abscission zones of floral organs, in the valve tissue of siliques and in young primary and lateral roots. The expression pattern of PLENTIFUL in younger roots appears to contradict a role in plant senescence but may be explained if PLENTIFUL has a role in tissue desiccation or nutrient cycling.
PLENTIFUL may be involved in nutrient mobilisation in senescing tissues and nutrient uptake in the root system.