The Dynamics of Flower Development in Castanea sativa Mill.

Maria Manuela Ribeiro Costa,Ana Teresa Alhinho,Miguel Jesus Nunes Ramos,Margarida Rocheta,Leonor Morais-Cecílio,José Gomes-Laranjo,Rómulo Sobral,Sofia Alves

doi:10.3390/plants10081538

Maria Manuela Ribeiro Costa, Ana Teresa Alhinho + Show 6 more

Open Access

https://doi.org/10.3390/plants10081538

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Abstract

The sweet chestnut tree (Castanea sativa Mill.) is one of the most significant Mediterranean tree species, being an important natural resource for the wood and fruit industries. It is a monoecious species, presenting unisexual male catkins and bisexual catkins, with the latter having distinct male and female flowers. Despite the importance of the sweet chestnut tree, little is known regarding the molecular mechanisms involved in the determination of sexual organ identity. Thus, the study of how the different flowers of C. sativa develop is fundamental to understand the reproductive success of this species and the impact of flower phenology on its productivity. In this study, a C. sativa de novo transcriptome was assembled and the homologous genes to those of the ABCDE model for floral organ identity were identified. Expression analysis showed that the C. sativa B- and C-class genes are differentially expressed in the male flowers and female flowers. Yeast two-hybrid analysis also suggested that changes in the canonical ABCDE protein–protein interactions may underlie the mechanisms necessary to the development of separate male and female flowers, as reported for the monoecious Fagaceae Quercus suber. The results here depicted constitute a step towards the understanding of the molecular mechanisms involved in unisexual flower development in C. sativa, also suggesting that the ABCDE model for flower organ identity may be molecularly conserved in the predominantly monoecious Fagaceae family.

Highlights

Development of unisexual male and female flowers has been regarded as a successful mechanism to decrease inbreeding by promoting cross-pollination and gene fluidity [1]
Castanea sativa is a monoecious species with an accentuated protandrous habit, as unisexual male catkins and bisexual catkins develop with a significant delay
Changes to the ABCDE model dynamics is proposed as one of the factors controlling the development of unisexual flowers by inception in several families, including the predominantly monoecious Fagaceae [4,33,34,35]

Summary

Introduction

Development of unisexual male and female flowers has been regarded as a successful mechanism to decrease inbreeding by promoting cross-pollination and gene fluidity [1]. The development of unisexual flowers has evolved, independently, multiple times, in some families being the predominant reproductive strategy Such is the case of the Fagaceae, a large plant family comprising more than 900 species that constitute an important economic resource and are pivotal to the dynamics of the forest ecosystems [2]. The ABCDE genes belong, predominantly, to the highly conserved MADS-box family. These genes encode for transcription factors with four domains: MADS (M), intervening (I), keratin-like (K), and C-terminal (C) [12]. The expression of one of the B-class genes, QsPISTILLATA (QsPI), determines the development of the male flower by establishing a complex with other B-class and C-class proteins. Complete lack of QsPI expression disables the obligatory heterodimerisation of the B-class protein complex, promoting carpel development [4]

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