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Background: Loropetalum subcordatum is an endangered species endemic to China that is characterized by narrow distribution, small population size, and delayed fertilization. However, the genetic diversity of the entire extant natural and ex situ populations has not been assessed to date. In this study, we evaluated the genetic diversity and structure of six natural populations and a single ex situ population (the only known ex situ population of L. subcordatum) using sequence-related amplified polymorphism data. Results: In total, 553 reliable DNA bands, of which 359 (63.28%) were polymorphic, were amplified by polymerase chain reaction with combinations of 15 primers. Low average gene diversity within populations and high genetic differentiation were detected in L. subcordatum. A Mantel test demonstrated that there was a positive correlation between genetic and geographic distances, indicating that significant genetic divergence was likely the result of geographic isolation among natural populations. Furthermore, based on genetic structure patterns, populations of L. subcordatum were divided into three clusters. Group 1 was composed of specimens from Libo, Guizhou Province (GZ) and Huanjiang, Guangxi Zhuang Autonomous Region (GX). Group 2 was composed of Mt. Wuguishan, Guangdong Province (GD). Group 3 was composed of three populations in Hong Kong Special Administrative Region. Additionally, clonal reproduction probably existed in GD population. According to the genetic information analysis and field survey, the ex situ population did not match its source population (GD) in terms of genetics, and its habitat was different from the original natural habitat. We observed that a few individual GD seeds were needed to improve ZS ex situ in the future. Conclusions: Compared to previous SRAP-based studies of endangered plants, L. subcordatum had extremely low average gene diversity within populations and high genetic differentiation among populations. At present, the unique ex situ population has not been successful due to non-representative samples being taken, a smaller population size, and man-made changes in habitat. Potential strategies are suggested to improve the conservation of this species. [ABSTRACT FROM AUTHOR]

Cultivated strawberry (Fragaria × ananassa) is a popular, economically important fruit. The ripening of the receptacle (pseudocarp), the main edible part, depends on endogenously produced abscisic acid (ABA) and is suppressed by the high level of auxin produced from achenes (true fruit) during early development. However, the mechanism whereby auxin regulates receptacle ripening through inhibiting ABA biosynthesis remains unclear. Here, we identified AUXIN RESPONSE FACTOR 2 (FaARF2), which showed decreased expression with reduced auxin content in the receptacle, leading to increased ABA levels and accelerated ripening. Dual-luciferase, yeast one-hybrid, and electrophoretic mobility shift assays demonstrated that FaARF2 could bind to the AuxRE element in the promoter of 9-CIS-EPOXYCAROT-ENOID DIOXYGENASE 1 (FaNCED1), a key ABA biosynthetic gene, to suppress its transcriptional activity. Transiently overexpressing FaARF2 in the receptacles decreased FaNCED1 expression and ABA levels, resulting in inhibition of receptacle ripening and of development of quality attributes, such as pigmentation, aroma, and sweetness. This inhibition caused by overexpressing FaARF2 was partially recovered by the injection of exogenous ABA; conversely, transient silencing of FaARF2 using RNA interference produced the opposite results. The negative targeting of FaNCED1 by FaARF2 is a key link between auxin-ABA interactions and regulation of strawberry ripening., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

Petals of the monocot Phalaenopsis aphrodite (Orchidaceae) possess conical epidermal cells on their adaxial surfaces, and a large amount of cuticular wax is deposited on them to serve as a primary barrier against biotic and abiotic stresses. It has been widely reported that subgroup 9A members of the R2R3-MYB gene family, MIXTA and MIXTA-like in eudicots, act to regulate the differentiation of conical epidermal cells. However, the molecular pathways underlying conical epidermal cell development and cuticular wax biosynthesis in monocot petals remain unclear. Here, we characterized two subgroup 9A R2R3-MYB genes, PaMYB9A1 and PaMYB9A2 (PaMYB9A1/2), from P. aphrodite through the transient overexpression of their coding sequences and corresponding chimeric repressors in developing petals. We showed that PaMYB9A1/2 function to coordinate conical epidermal cell development and cuticular wax biosynthesis. In addition, we identified putative targets of PaMYB9A1/2 through comparative transcriptome analyses, revealing that PaMYB9A1/2 acts to regulate the expression of cell wall-associated and wax biosynthetic genes. Furthermore, a chemical composition analysis of cuticular wax showed that even-chain n-alkanes and odd-chain primary alcohols are the main chemical constituents of cuticular wax deposited on petals, which is inconsistent with the well-known biosynthetic pathways of cuticular wax, implying a distinct biosynthetic pathway occurring in P. aphrodite flowers. These results reveal that the function of subgroup 9A R2R3-MYB family genes in regulating the differentiation of epidermal cells is largely conserved in monocots and dicots. Furthermore, both PaMYB9A1/2 have evolved additional functions controlling the biosynthesis of cuticular wax., (© The Author(s) 2021. Published by Oxford University Press on behalf of American Society of Plant Biologists.)