The timing of flowering and the inflorescence architecture are critical for the reproductive success of tomato (Solanum lycopersicum), but the gene regulatory networks underlying these traits have not been fully explored. Here, we show that the tomato FRUITFULL-like (FUL-like) genes FUL2 and MADS-BOX PROTEIN 20 (MBP20) promote the vegetative-to-reproductive transition and repress inflorescence branching by inducing floral meristem (FM) maturation. FUL1 fulfils a less prominent role and appears to depend on FUL2 and MBP20 for its upregulation in the inflorescence- and floral meristems. MBP10, the fourth tomato FUL-like gene, has probably lost its function. The tomato FUL-like proteins cannot homodimerize in in vitro assays, but heterodimerize with various other MADS-domain proteins, potentially forming distinct complexes in the transition meristem and FM. Transcriptome analysis of the primary shoot meristems revealed various interesting downstream targets, including four repressors of cytokinin signaling that are upregulated during the floral transition in ful1 ful2 mbp10 mbp20 mutants. FUL2 and MBP20 can also bind in vitro to the upstream regions of these genes, thereby probably directly stimulating cell division in the meristem upon the transition to flowering. The control of inflorescence branching does not occur via the cytokinin oxidase/dehydrogenases (CKXs) but may be regulated by repression of transcription factors such as TOMATO MADS-box gene 3 (TM3) and APETALA 2b (AP2b).

Successful plant reproduction and fruit formation depend on adequate pollen and pistil development, and pollen–pistil interactions. In Nicotiana tabacum, pollen tubes grow through the intercellular spaces of pistil-specialized tissues, stigmatic secretory zone, and stylar transmitting tissue (STT). These intercellular spaces are supposed to be formed by the modulation of cell wall pectin esterification. Previously we have identified a gene preferentially expressed in pistils encoding a putative pectin acetylesterase (PAE), named NtPAE1. Here, we characterized the NtPAE1 gene and performed genome-wide and phylogenetic analyses of PAEs. We identified 30 PAE sequences in the N. tabacum genome, distributed in four clades. The expression of NtPAE1 was assessed by RT-qPCR and in situ hybridization. We confirmed NtPAE1 preferential expression in stigmas/styles and ovaries and demonstrated its high expression in the STT. Structural predictions and comparisons between NtPAE1 and functional enzymes validated its identity as a PAE. Transgenic plants were produced, overexpressing and silencing the NtPAE1 gene. Overexpressed plants displayed smaller flowers while silencing plants exhibited collapsed pollen grains, which hardly germinate. NtPAE1 silencing plants do not produce fruits, due to impaired pollen tube growth in their STTs. Thus, NtPAE1 is an essential enzyme regulating pectin modifications in flowers and, ultimately, in plant reproduction.

The effector molecule is a short RNA duplex, composed of two strands of approximately 21 nucleotides, with two overhanging bases at the 3’ end (^{Elbashir et al., 2001}). However, several types of precursors can trigger gene silencing, such as long double-stranded RNAs (dsRNAs) from 200 to 800 base pairs (bp) (^{Guo et al., 2018}), hairpin RNAs (hpRNAs) (^{Hussain et al., 2019}), small interfering RNAs (siRNAs) (^{Guo et al., 2018}), short hairpin RNAs (shRNAs) (^{Wang et al., 2018}), among others. Notoriously, an ingenious and inexpensive way to produce shRNAs in large quantities was developed, via in vitro transcription of a circularized DNA template, generating multimeric shRNAs (mshRNAs) (^{Seyhan et al., 2006}; ^{Abe et al., 2012}). In the last decade, such multimeric shRNAs generated by rolling circle transcription have been used by other groups and have been shown to be an interesting option for RNAi (^{Wang et al., 2015}; ^{Shopsowitz et al., 2016}; ^{Wu et al., 2016}; ^{Kim et al., 2018}).^{7 8}

In the Nicotiana tabacum flower development study, we identified SCI1 (Stigma/style Cell-cycle Inhibitor 1), a regulator of cell proliferation. SCI1 interacts with NtCDKG;2 (N. tabacum Cyclin-Dependent Kinase G;2), a homolog of human CDK11, which is responsible for RanGTP-dependent microtubule stabilization, regulating spindle assembly rate. In a Y2H screening of a cDNA library using NtCDKG;2 as bait, a RanBP1 (Ran-Binding Protein 1) was revealed as its interaction partner. RanBP1 is an essential regulatory protein of the RanGTPase system, contributing to the formation of the Ran gradient, which modulates different important cellular processes. RanBP1 is crucial in the nuclear import/export machinery during interphase and spindle checkpoint formation during cell division. These processes are well studied in animals, but very little is known about them in plants. We confirmed NtCDKG;2 and NtRanBP1 interaction by pairwise Y2H and characterized the localization of both proteins during plant cell division. We demonstrated the presence of NtRanBP1 in the cytoplasm during interphase and its nuclear arrest at mitosis onset. Meanwhile, we showed that NtCDKG;2 is localized in the mitotic spindle during cell division, indicating an analogous function to the human CDK11. We propose that the phosphorylation of the nuclear export signal at RanBP1 by NtCDKG;2 may be responsible for the reported nuclear arrest.

Exposure to hypergravity can alter the viability, morphology, development and behavior of living beings. Thus, the analysis of these factors is essential when considering life on supermassive planets, as well as in 'ballistic panspermia' scenarios related to the ejection of rocks from the surface of a planet, which could serve as transfer vehicles to spread the life between planets within a solar system. Studies analyzing the effects of hypergravity regimes are abundant in the literature, however, only a few researches carried out experiments using conditions of the order of 105 x g. In addition, the only plant species tested so far, as an entire structure instead of detached parts, exposed to gravity stress of this order of magnitude in its entirety was Oryza sativa, whose seeds were able to germinate after being exposed to 450,000 x g. Recently, our research group demonstrated that some free-living nematode species can support 400,000 x g. In the present study, we report that seeds of the plant model Nicotiana benthamiana exposed to 400,000 x g for 1h are able to germinate into fully normal young seedlings, with no apparent morphological alterations. Since N. benthamiana is used in laboratories worldwide and an easy to cultivate plant model, theoretical and experimental models of lithopanspermia and life in supermassive planets may benefit from it.