Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/20/2007
Publication Date: 12/1/2007
Citation: Zhang, Z., Simons, K.J., Gill, B.S., Faris, J.D. 2007. Exploring the functional roles of the Q gene homoeoalleles in wheat. Meeting Abstract. National Wheat Genomics Abstracts pg. 6
Technical Abstract: The Q gene on chromosome 5A (Q-A1) has been referred to as a super gene in wheat because it governs the free-threshing character and square spike phenotype. It also pleiotropically affects many other traits associated with wheat development and domestication. The function of the Q homoeoalleles on chromosomes 5B (q-B1) and 5D (q-D1) is less understood. In this study, we further investigated the function of Q-A1 through comparison of the wild type Q-A1 allele with an EMS-induced Q-A1-knockout mutant in the hexaploid wheat cultivar Bobwhite. The phenotypic comparison confirmed the numerous pleiotropic effects of Q-A1. Relative quantitative-PCR (RQ-PCR) analysis revealed that the mutant allele, which has a premature stop codon, was transcribed at a lower level than the wild type. This result provided additional evidence that the amino acid at position 329 is important for homodimer formation, which may be a mechanism of self-regulation. We also initiated the functional analysis of the q homologs on 5B and 5D chromosomes. The genomic and cDNA sequences of Q-A1, q-B1 and q-D1 share >90% similarity. Chinese Spring (CS) q-B1 and q-D1 deletion lines (5BL-14 and 5DL-5) had semi-speltoid spikes instead of square spikes as observed in euploid CS. We developed a double deletion line lacking both Q-A1 and q-D1, which exhibited more extreme speltoid spikes and tougher glumes compared to the single gene deletion lines. In addition, alternatively spliced transcriptional variants were found for both q-B1 and q-D1 in spike tissues. Specific RQ-PCR assays were developed for each homoeoallele and their transcriptional variants, and the results suggested the presence of complex interactions among the homoeoalleles. This study demonstrated that the q homoeoalleles on 5B and 5D contributed to the suppression of speltoid characters and glume toughness, but to a lesser degree than does the Q-A1 allele on 5A. The mutation in q-A1 that gave rise to Q-A1 played a key role in the modern wheat evolution.