SUMMARY
Plant species with large genomes tend to be excluded from climatically more extreme environments with a shorter growing season. Species that occupy such environments are assumed to be under ...natural selection for more rapid growth and smaller genome size (GS). However, evidence for this is available only for temperate organisms. Here, we study the evolution of GS in two subfamilies of the tropical family Zingiberaceae to find out whether species with larger genomes are confined to environments where the vegetative season is longer. We tested our hypothesis on 337 ginger species from regions with contrasting climates by correlating their GS with an array of plant traits and environmental variables. We revealed 16‐fold variation in GS which was tightly related to shoot seasonality. Negative correlations of GS with latitude, temperature and precipitation emerged in the subfamily Zingiberoidae, demonstrating that species with larger GS are excluded from areas with a shorter growing season. In the subfamily Alpinioideae, GS turned out to be correlated with the type of stem and light requirements and its members cope with seasonality mainly by adaptation to shady and moist habitats. The Ornstein–Uhlenbeck models suggested that evolution in regions with humid climates favoured larger GS than in drier regions. Our results indicate that climate seasonality exerts an upper constraint on GS not only in temperate regions but also in the tropics, unless species with large genomes find alternative ways to escape from that constraint.
Significance Statement
The question of how species can adapt to periods of drought and drought stress is of great relevance in the current period of climate change and it is also worth asking whether mechanisms of adaptation are similar in different parts of the world. Here, we focused on the poorly understood but complex biomes like monsoon forest, tropical dry forest and tropical rainforest, while using the economically important family Zingiberaceae as a model group.
Abstract
γ-Tubulin is associated with microtubule nucleation, but evidence is accumulating in eukaryotes that it functions also in nuclear processes and in cell division control that are independent ...of its canonical role. We found that in Arabidopsis thaliana γ-tubulin interacts specifically with E2FA, E2FB, and E2FC transcription factors both in vitro and in vivo. The interaction of γ-tubulin with the E2Fs is not reduced in the presence of the dimerization partners (DPs) and, in agreement, we found that γ-tubulin interaction with E2Fs does not require the dimerization domain. γ-Tubulin associates with the promoters of E2F-regulated cell cycle genes in an E2F dependent manner, likely in complex with the E2F/DP heterodimer. The upregulation of E2F targets; PCNA, ORC2, CDKB1;1 and CCS52A under γtubulin silencing suggests a repressive function for γ-tubulin at G1/S, G2/M and endocycle, which is consistent with an excess of cell division in some cells and enhanced endoreduplication in others in the shoot and young leaves of γ-tubulin RNAi plants. Altogether, our data show ternary interaction of γ-tubulin with E2F/DP heterodimer and suggest a repressive role for γ-tubulin with E2Fs in controlling mitotic activity and endoreduplication during plant development.
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