Differential expression of proteins in maize roots in response to abscisic acid and drought

Roots are highly sensitive organ in plant response to drought, which commonly inhibits root growth. However, less is known about the effect of ABA on root protein expression induced by drought. To help clarify the role of ABA in protein expression of root response to drought, root protein patterns were monitored using a proteomic approach in maize ABA-deficient mutant vp5 and its wild-type Vp5 exposed to drought. Two-dimensional electrophoresis was used to identify drought-responsive protein spots in maize roots. After coomassie brilliant blue staining, approximately 450 protein spots were reproducibly detected on each gel, wherein 22 protein spots related to ABA or drought were identified using MALDI-TOF MS. Results showed that the 22 proteins are involved in such several cellular processes as energy and metabolism, redox homeostasis and regulatory. An anionic peroxidase and two putative uncharacterized proteins were up-regulated by drought in ABA-dependent way; A glycine-rich RNA binding protein 2, pathogenesis-related protein 10, an enolase, a serine/threonine-protein kinase receptor and a cytosolic ascorbate peroxidase were up-regulated by drought in both ABA-dependent and ABA-independent way; a nuclear transport factor 2, a nucleoside diphosphate kinase, a putative uncharacterized protein and a peroxiredoxin-5 were up-regulated by drought in ABA-independent way; a superoxide dismutase 4A, a VAP27-2, a transcription factor BTF3, a glutathione S-transferase GSTF2 and a putative uncharacterized protein were up-regulated by drought in ABA-dependent way, but not exogenous ABA treatment in the absence of drought; a O-methyltransferase and a putative uncharacterized proteins were down-regulated by ABA and drought. The identification of some novel proteins in the drought response provides new insights that can lead to a better understanding of the molecular basis of root drought tolerance.