Transcriptional, metabolic, physiological and developmental responses of
switchgrass to phosphorus limitation.
Abstract
Knowing how switchgrass (Panicum virgatum L.) responds and adapts
to phosphorus (P)-limitation will aid efforts to optimize P-efficiency
in this species for sustainable biomass production. This integrative
study investigated the impacts of mild, moderate, and severe P-stress on
genome transcription and whole-plant metabolism, physiology and
development in an unprecedented way for this species. P-limitation
reduced overall plant growth, increased root/shoot ratio, increased root
branching at moderate P-stress, and decreased root diameter with
increased density and length of root hairs at severe P-stress. RNA-seq
analysis revealed thousands of genes that were differentially expressed
under moderate and severe P-stress in roots and/or shoots compared to
P-replete plants, with many stress-induced genes involved in
transcriptional and other forms of regulation, primary and secondary
metabolism, transport, and other processes involved in P-acquisition and
homeostasis. Amongst the latter were multiple miRNA399 genes and
putative targets of these. Metabolite profiling showed that levels of
most sugars and sugar alcohols decreased with increasing P stress, while
organic and amino acids increased under mild and moderate P-stress in
shoots and roots, although this trend reversed under severe P-stress,
especially in shoots.