Abstract
Abscisic acid (ABA) plays an essential role in root hair elongation in plants, but the regulatory mechanism remains to be elucidated. In this study, we found that exogenous ABA can promote rice root hair elongation. Transgenic rice overexpressing SAPK10 (Stress/ABA-activated protein kinase 10) had longer root hairs; rice plants overexpressing OsABIL2 (OsABI-Like 2) had attenuated ABA signaling and shorter root hairs, suggesting that the effect of ABA on root hair elongation depends on the conserved PYR/PP2C/SnRK2 ABA signaling module. Treatment of the DR5-GUS and OsPIN-GUS lines with ABA and an auxin efflux inhibitor showed that ABA-induced root hair elongation depends on polar auxin transport. To examine the transcriptional response to ABA, we divided rice root tips into three regions: short root hair, long root hair and root tip zones; and conducted RNA-seq analysis with or without ABA treatment. Examination of genes involved in auxin transport, biosynthesis and metabolism indicated that ABA promotes auxin biosynthesis and polar auxin transport in the root tip, which may lead to auxin accumulation in the long root hair zone. Our findings shed light on how ABA regulates root hair elongation through crosstalk with auxin biosynthesis and transport to orchestrate plant development.
Highlights
Roots have important functions in uptake of nutrients and water, and anchoring plants in the soil
We found that most root hairs initiated in the region about 3 mm from the root apex under normal growth conditions, but most root hairs initiated in the region about 0.2 mm from the apex in roots treated with 2 μM Abscisic acid (ABA) for 24 h
We measured the root hair length which located 4–5 mm distant from root apex in Figure 1D, this because considering the several ABA concentration treatment of root hair phenotype, we found that the best region to measure root hair length located at 4–5 mm distant from root tip
Summary
Roots have important functions in uptake of nutrients and water, and anchoring plants in the soil. Extensions from single root epidermal cells, constitute up to an estimated 70% of the root surface area in crops (Richardson et al, 2009; Pereg and McMillan, 2015). Root hairs play important roles in the uptake and transport of NO3− and NH4+ (Gilroy and Jones, 2000). A root 1 mm in diameter with root hairs 0.5 or 1 mm in average length, growing in sand, will improve the soil water uptake rate by 30 to 55% in barley (Segal et al, 2008)
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