Adaptive evolution of benzoxazinoids in wild emmer wheat, Triticum dicoccoides, at "Evolution Canyon", Mount Carmel, Israel

Abstract

Background"Evolution Canyon" (ECI) at Lower Nahal Oren, Mount Carmel, Israel, is an optimal natural microscale model for unraveling evolution-in-action, highlighting the evolutionary processes of biodiversity evolution, adaptation, and incipient sympatric speciation. A major model organism in ECI is the tetraploid wild emmer wheat, Triticum dicoccoides (TD), the progenitor of cultivated emmer and durum wheat. TD displays dramatic interslope adaptive evolutionary divergence on the tropical, savannoid-hot and dry south-facing, "African" slope (AS), and on the temperate, forested, cool and humid, north-facing, "European" slope (ES), separated on average by 250 m. From the perspective of chemical evolution and metabolomics, it is important to unravel interslope divergence in biologically relevant secondary metabolites between the abutting slope populations. Here, in TD we examined hydroxamic acid (Hx), which is a family of secondary cereal metabolites, and plays a major role in defending the plant against fungi, insects and weeds.ResultsOur examination revealed that higher concentrations of DIBOA and DIMBOA were found in seedlings growing in the same greenhouse from seeds collected from the cool and humid forested ES, whereas the seedlings of seeds collected from the savannoid AS (both in root and shoot tissues), showed no DIMBOA. Remarkably, only DIBOA appears in both shoots and roots of the AS seedlings. It rises to a peak and then decreases in both organs and in seedlings from both slopes. The DIMBOA, which appears only in the ES seedlings, rises to a peak and decreases in the shoot, but increased and remained in a plateau in the root, till the end of the experiment.Conculsions/SignificanceThe results suggest stronger genetic resistance of defense compounds DIBOA and DIMBOA against biotic stresses (fungi and other pathogens) by ES seedlings. However, AS seedlings responded earlier but were to the same biotic stresses. The genetic difference found in AS seedlings was caused by the main adaptive selection in AS, which was against climatic, abiotic stresses, and was weaker, or not at all, against biotic stresses. The distinct genetic interslope differences appear important and is very significant and are elaborated in the discussion.

Cereal aphids differently affect benzoxazinoid levels in durum wheat

“…avenae aphid, and it also highly accumulated HDMBOA-Glc (Figs 1 and 3B). Although DIMBOA levels were only slightly over-accumulated, it constitutes the predominant benzoxazinoid in wheat seedlings (Fig 4)[63]. The constitutive and herbivore-induced, specifically by cereal aphids, benzoxazinoid levels should be further explored to discover the corresponding genes involved in this pathway, mainly the unknown Bx6 , Bx7 and Bx10-Bx14 genes.…”

The Roots of Rye (Secale cereale L.) Are Capable of Synthesizing Benzoxazinoids

“…Many studies on different aspects BX biosynthesis over the past 50 years have reported that this class of metabolites is present in roots, root exudates, or root extracts of such species as maize [ 6 , 21 , 22 , 23 ], common wheat [ 24 , 25 , 26 , 27 ], emmer wheat [ 28 ], and rye [ 2 , 14 , 15 , 16 , 24 , 29 ]. Additionally, transcripts of Bx1 , the first gene controlling the BX biosynthesis pathway, have been detected in roots of rye [ 10 , 14 , 15 , 16 ], wheat [ 17 ], and maize [ 18 , 19 ].…”

Biosynthesis of benzoxazinoids in rye (Secale cerealeL.) – where does the story begin?

“…The copyright holder for this preprint this version posted March 5, 2021. ; https://doi.org/10.1101/2021.03.05.434075 doi: bioRxiv preprint 1 1 wheat (Ben-Abu et al, 2018), and rye (Pérez and Ormenoñuñez 1991, Zasada et al, 2007, Schulz et al, 2013, Rakoczy-Trojanowska et al, 2018aRakoczy-Trojanowska et al, 2020). Also, transcripts of Bx1, the first gene controlling the BX biosynthesis pathway, have been detected in roots of rye (Tanwir et al, 2017, Rakoczy-Trojanowska et al, 2018a, b, 2020, wheat (Nomura et.…”

“…Many studies on different aspects BX biosynthesis over the past 50 years have reported that this class of metabolites is present in roots, root exudates, or root extracts of such species as maize (Neal et al, 2012, Neal and Ton 2013, Handrick et al, 2016; Cotton et al, 2019), common wheat (Pérez and Ormenoñuñez 1991, Belz and Hurle 2005, Stochmal et al, 2006, Villagrasa et al, 2006), emmer wheat (Ben-Abu et al, 2018), and rye (Pérez and Ormenoñuñez 1991, Zasada et al, 2007, Schulz et al, 2013, Rakoczy-Trojanowska et al, 2018a, b; Rakoczy-Trojanowska et al, 2020). Also, transcripts of Bx1 , the first gene controlling the BX biosynthesis pathway, have been detected in roots of rye (Tanwir et al, 2017, Rakoczy-Trojanowska et al, 2018a, b, 2020), wheat (Nomura et.…”