Unisexual flower initiation in the monoecious Quercus suber L.: a molecular approach

Abstract

<jats:title>Abstract</jats:title> <jats:p>Several plant species display a temporal separation of the male and female flower organ development to enhance outbreeding; however, little is known regarding the genetic mechanisms controlling this temporal separation. Quercus suber is a monoecious oak tree with accentuated protandry: in late winter, unisexual male flowers emerge adjacent to the swollen buds, whereas unisexual female flowers emerge in the axils of newly formed leaves formed during spring (4–8 weeks after male flowering). Here, a phylogenetic profiling has led to the identification of cork oak homologs of key floral regulatory genes. The role of these cork oak homologs during flower development was identified with functional studies in Arabidopsis thaliana. The expression profile throughout the year of flower regulators (inducers and repressors), in leaves and buds, suggests that the development of male and female flowers may be preceded by separated induction events. Female flowers are most likely induced during the vegetative flush occurring in spring, whereas male flowers may be induced in early summer. Male flowers stay enclosed within the pre-dormant buds, but complete their development before the vegetative flush of the following year, displaying a long period of anthesis that spans the dormant period. Our results portray a genetic mechanism that may explain similar reproductive habits in other monoecious tree species.</jats:p>

Population structure in Quercus suber L. revealed by nuclear microsatellite markers

“…Another possible explanation for low heterozygosity and positive F IS is positive assortative mating, of which self-fertilization is an extreme case ( Waples, 2015 ). Selfing is expected to occur to some extent in monoecious species, although Q. suber is known to have dichogamous flower development, which promotes outcrossing ( Sobral et al, 2020 ).…”

Reproduction alternation in trees: testing the resource depletion hypothesis using experimental fruit removal inQuercus ilex

“…Q. ilex has preformed buds (Montserrat-Martí et al 2009). A recent study on its close relative Q. suber showed that male flowers are preformed and induced in the early summer of the previous year, whereas female flowers are most likely induced during the vegetative flush in spring (Sobral et al 2020). Similarly, the basal part of the shoots is preformed in Q. ilex while their distal part is very likely neoformed (Y. Caraglio, personal communication).…”

Molecular control of dormancy transitions throughout the year in the monoecious cork oak

“…The environmental parameters required for growth cessation and bud swelling in Q. suber remain poorly known (Pinto et al ., 2011). Q. suber presents a complex bud biology, making it difficult to predict the exact timing of bud dormancy release and flower emergence (Sobral et al ., 2020). In summer, during bud development and before growth cessation, male inflorescence primordia differentiate inside the bud (Sobral et al ., 2020).…”

“…Q. suber presents a complex bud biology, making it difficult to predict the exact timing of bud dormancy release and flower emergence (Sobral et al ., 2020). In summer, during bud development and before growth cessation, male inflorescence primordia differentiate inside the bud (Sobral et al ., 2020). Usually during September/October, Q. suber bud set and shoot growth cessation occurs, lasting until the end of winter or early spring, when bud swelling occurs simultaneously with the emergence of male flowers.…”