Roothairless5, which functions in maize (Zea maysL.) root hair initiation and elongation encodes a monocot‐specificNADPHoxidase

Abstract

SUMMARYRoot hairs are instrumental for nutrient uptake in monocot cereals. The maize (Zea mays L.) roothairless5 (rth5) mutant displays defects in root hair initiation and elongation manifested by a reduced density and length of root hairs. Map-based cloning revealed that the rth5 gene encodes a monocot-specific NADPH oxidase. RNA-Seq, in situ hybridization and qRT-PCR experiments demonstrated that the rth5 gene displays preferential expression in root hairs but also accumulates to low levels in other tissues. Immunolocalization detected RTH5 proteins in the epidermis of the elongation and differentiation zone of primary roots. Because superoxide and hydrogen peroxide levels are reduced in the tips of growing rth5 mutant root hairs as compared with wild-type, and Reactive oxygen species (ROS) is known to be involved in tip growth, we hypothesize that the RTH5 protein is responsible for establishing the high levels of ROS in the tips of growing root hairs required for elongation. Consistent with this hypothesis, a comparative RNA-Seq analysis of 6-day-old rth5 versus wild-type primary roots revealed significant over-representation of only two gene ontology (GO) classes related to the biological functions (i.e. oxidation/reduction and carbohydrate metabolism) among 893 differentially expressed genes (FDR <5%). Within these two classes the subgroups 'response to oxidative stress' and 'cellulose biosynthesis' were most prominently represented.

Root Hair Development in the Grasses: What We Already Know and What We Still Need to Know

“…Finally, in situ mRNA hybridization experiments have shown that the transcription of HvPEROXIDASE45 is restricted to individual root epidermal cells (Kwasniewski et al, 2013a). In maize, the gene RTH5 encodes a grass species-specific NADPH oxidase; its loss-of-function mutation resulted in a marked drop in both RH density and RH length (Nestler et al, 2014). The phenotype can be related to a reduced accumulation of ROS in the trichoblasts.…”

ROS Regulation of Polar Growth in Plant Cells

“…Two NOXs (AtNOXH and AtNOXJ) have been implicated in pollen tube tip expansion and fertilization (Boisson-Dernier et al, 2013;Kaya et al, 2014;Lassig et al, 2014) and one NOX (AtNOXC, named ROOT HAIR DEFECTIVE [RHD2]) in root hair tip growth (Fig 1; Foreman et al, 2003;Takeda et al, 2008). Recently, a monocot NOX named RTH5 (from maize [Zea mays]), with high sequence similarity to AtNOXH and AtNOXJ, was identified as an important player in the transition between root hair bulge formation and tip growth (Nestler et al, 2014).…”

Genome-wide association studies of doubled haploid exotic introgression lines for root system architecture traits in maize (Zea mays L.)

“…Several genes which affect root development in maize have also been identified: rtcs (rootless concerning crown and seminal roots), rth1 (roothairless 1), rth2 (roothairless 2), rth3 (roothairless 3), rth5 (roothairless 5) and rum1 (rootless with undetectable meristems 1). The gene rtcs controls crown root and seminal root formation [6] rth1, rth2, rth3, and rth5 control root hair elongation in maize [7][8][9][10], and rum1 controls lateral root growth and seminal root growth [11]. In addition, rth3 has also been shown to affect grain yield in maize [9].…”