Characterization of LRL5 as a key regulator of root hair growth in maize

Abstract

Root hair, a special type of tubular-shaped cell, outgrows from the root epidermal cell and plays important roles in the acquisition of nutrients and water, as well as interactions with biotic and abiotic stresses. Studies in the model plant Arabidopsis have revealed that root-hair initiation and elongation are hierarchically regulated by a group of basic helixÀloopÀhelix (bHLH) transcription factors (TFs). However, knowledge regarding the regulatory pathways of these bHLH TFs in controlling root hair growth remains limited. In this study, RNA-seq analysis was conducted to profile the transcriptome in the elongating maize root hair and >1000 genes with preferential expression in root hair were identified. A consensus cis-element previously featured as the potential bHLH-TF binding sites was present in the regulatory regions for the majority of the root hairpreferentially expressed genes. In addition, an individual change in ZmLRL5, the highest-expressed bHLH-TF in maize root hair resulted in a dramatic reduction in the elongation of root hair, and rendered the growth of root hair hypersensitive to translational inhibition. Moreover, RNA-seq, yeast-one-hybrid and ribosome profile analysis suggested that ZmLRL5 may function as a key player in orchestrating the translational process by directly regulating the expression of translational processes/ribosomal genes during maize root hair growth.

Co-Expression of ZmVPP1 with ZmNAC111 Confers Robust Drought Resistance in Maize

“…It is therefore likely that developing a relatively deep and strong root system can facilitate water uptake from deeper in the soil, potentially increasing survival rates at the seedling stage [32]. Overexpression of the root developmental regulators ZmVPP1, ZmTIP1, or ZmLRL5 can promote root development, resulting in increased root biomass and root hair elongation, and greater resistance to drought conditions [16,19,42]. In the pyramided lines generated here, both root development and root-shoot ratio were increased over that in WT, which could at least partially explain the observed drought resistance in seedlings (Figure 3), and could enable surviving seedlings to thrive after water was replenished.…”

Genome-wide association study reveals the genetic architecture of root hair length in maize

“…Maize seeds were surface-sterilized in a 10% NaClO solution for 5 min, rinsed several times with distilled water, and germinated in moist germination paper rolls (Anchor Paper) at 28 °C under constant darkness as previously described [ 25 ]. The root hair length of primary roots from 3-day-old plants were captured using stereo microscope.…”

“…The ZmLRL5 gene, encoding a basic helix–loop–helix (bHLH) transcription factor, was demonstrated to play a positive role in orchestrating the translational process by directly regulating the expression of translational processes/ribosomal genes during maize root hair growth. The loss-of-function of ZmLRL5 resulted in a dramatic reduction in the elongation of root hair [ 25 ]. Recently, ZmTIP1 , encoding a functional S-acyltransferase, was identified to participate in drought tolerance by regulating root hair growth [ 26 ].…”

Striking a growth–defense balance: Stress regulators that function in maize development

“…This idea is supported by the significant downregulation of numerous cellulose biosynthesis‐related genes in the primary roots of rth5 compared with wild‐type plants, particularly Rth6 , which encodes a cellulose synthase essential for root hair elongation (Li et al, 2016). Although six genes regulating root hair growth have been identified in maize, all of which govern root hair elongation, only Rth5 also regulates root hair initiation (Wen et al, 2005; Hochholdinger et al, 2008; Nestler et al, 2014; Li et al, 2016; Wang et al, 2019; Zhang et al, 2020). It would be intriguing to explore the specific mechanisms by which Rth5 drives root hair initiation, especially considering the lack of significant cytological differences between trichoblast and atrichoblast cells in the maize root epidermis (Clowes, 2000).…”