Читать книгу Biotechnology of Fruit and Nut Crops - Группа авторов - Страница 140

Adam et al. (2011) reviewed the current status of those factors that regulate gender plasticity in the oil palm, which has the overall effect of promoting the production of male inflorescences in response to water deficit and other stresses, whereas female flowering is favoured when growing conditions are optimal. The slow development of the oil palm inflorescence, which is usually 2–3 years between initiation and maturity, renders studies complicated. However, the flowering of this species in response to stress provides a useful experimental system whereby regulation of sex determination can be studied (Adam et al., 2005). Functional genomic approaches will provide information on the fundamental processes that underlie sex determination in oil palm.

MADS box genes code for a large family of transcription factors which regulate development in higher plants, notably flower formation. Adam et al. (2006, 2007) described members of the MADS box gene family in the oil palm. The authors identified and characterized 13 oil palm MADS box genes which were found to belong to five different subfamilies, i.e. the previously defined SQUAMOSA, AGAMOUS, AGAMOUS-like2, DEFICIENS and GLOBOSA groups. Genes belonging to each of these groups play a critical role in the determination of flower structure as defined by the ABCDE model. Sex ratio (SR), the ratio of female inflorescences to total inflorescences, is one of the main yield components of oil palm. The SR QTL was recently identified on linkage (LG) 8 with a phenotype variance explained (PVE) of 11.3%. The use of both genetic and physical mapping is one the strategies for uncovering the genetic basis of the traits. Somyong et al. (2015) constructed bacterial artificial chromosome (BAC) and fosmid libraries, which were used for physical mapping in oil palm. Once combined, the libraries consisted of >200,000 clones, representing 6.35 genome equivalents. Physical mapping at the SR locus was implemented by incorporating the published oil palm genome sequence and positive BAC/fosmid clones as identified by colony PCR screening. As a result, a putative aldo-keto reductase gene (named EgAKR1) was revealed to be a promising candidate for SR determination, via controlling female inflorescence number (11% of PVE). This was predicted from the two newly identified polymorphic marker loci (mEgSSRsr8-21LB and mEgAKR1-9) designed from EgAKR1. The functions of AKR gene families in other plant species and subsequent promoter analysis suggested that EgAKR1 may contribute to the SR through abiotic stress responsiveness.