A root-specific wall-associated kinase gene, HvWAK1, regulates root growth and is highly divergent in barley and other cereals

Abstract

Wall-associated receptor-like kinases (WAKs) are important candidates for directly linking the extracellular matrix with intracellular compartments and are involved in developmental processes and stress response. WAK gene family has been identified in plants such as Arabidopsis and rice. Here, we present a detailed analysis of the WAK1 gene from barley cv. Golden Promise, mapped to chromosome 5H. Three BAC clones corresponding to the WAK fragment were sequenced and the full-length WAK1 gene was characterized. The gene has three exons and two short introns with a coding region of 2,178 bp encoding a protein of 725 amino acids. A regulatory region was analyzed in -1,000 bp sequence upstream to start codon. Using conserved domains database and SMART, various conserved domains such as GUB WAK Bind, epidermal growth factor CA, and protein kinase C as well as other regions like signal peptides, active sites, and transmembrane domains were identified. The gene organization of HvWAK1 was compared with wheat (TaWAK1) and Arabidopsis (AtWAK1), suggesting that the WAK1 gene organization has remained highly conserved. Nonetheless, WAK1 was found to be highly divergent when compared with sequences available from barley cv. Haruna Nijo (50 %), rice (46 %), wheat (21 %), Arabidopsis (25 %), and maize (19 %). This divergence may have facilitated a better adaptation to surrounding environments due to its role in communication between the extracellular matrix, cell, and outer environment. Semiquantitative RT-PCR-based expression analysis indicates HvWAK1 expression is specific to roots. Significant differences in root growth between GP wild type and GP-Ds mutant seedlings were observed under control and salt stress conditions.

Duplicate and Conquer: Multiple Homologs ofPHOSPHORUS-STARVATION TOLERANCE1Enhance Phosphorus Acquisition and Sorghum Performance on Low-Phosphorus Soils

“…Indeed, expression of WAK1 in Arabidopsis was found to be induced by aluminum treatment (Sivaguru et al, 2003), and WAKL4 is related to mineral nutrition responses (Hou et al, 2005). Wall-associated kinases are necessary for normal cell enlargement (Cosgrove, 2001;Wagner and Kohorn, 2001), and in barley and rice, WAK genes were found to affect root growth Gupta, 2008, 2011;Kaur et al, 2013). Our results indicate that multiple SNPs within Sb03g006765 are consistently associated with sorghum performance under low P in the two association panels.…”

“…These features are typical of cytoplasmic Ser/Thr wall-associated kinase (WAK) proteins, which span the plasma membrane and extend to the extracellular region to bind tightly to the cell wall (He et al, 1999). According to our sequence data, all selected sorghum SbPSTOL1 genes possess three exons and two introns, which is the typical intron-exon organization of Arabidopsis (He et al, 1999;Kanneganti and Gupta, 2008), barley (Hordeum vulgare; Kaur et al, 2013), and rice (Zhang et al, 2005) WAKs. In addition, five highly similar WAK genes were found to lie in a 30-kb cluster in Arabidopsis (He et al, 1999), which resembles the genome organization of the SbPSTOL1 genes at position 60 Mb on chromosome 3.…”

The maize disease resistance gene Htn1 against northern corn leaf blight encodes a wall-associated receptor-like kinase

“…Wall-associated kinases have been found to play a role in disease resistance (30,31), phosphorus-starvation tolerance (32), and developmental processes such as root growth (33) and gametophyte development (34). A recent study reported that the maize quantitative head smut resistance gene qHSR1 also encodes a wall-associated kinase.…”

Fungal resistance mediated by maize wall‐associated kinase ZmWAK‐RLK1 correlates with reduced benzoxazinoid content

“…For instance, in rice > 100 members were found (Zhang et al ., ; Kanneganti & Gupta, ). A number of WAK genes in monocots have been shown to be associated to several functional aspects, such as biotic diseases (Li et al ., ; Hurni et al ., ; Zuo et al ., ; Shi et al ., ; Hu et al ., ), tolerance to phosphorus deficiency (Hufnagel et al ., ), root growth (Kaur et al ., ), as well as gametophyte development (Wang et al ., ). WAKs are the only known proteins that physically link the cell wall to the plasma membrane (Brutus et al ., ; Kohorn & Kohorn, ).…”