Altered expression of maize PLASTOCHRON1 enhances biomass and seed yield by extending cell division duration

Maize is the highest yielding cereal crop grown worldwide for grain or silage. Here, we show that modulating the expression of the maize PLASTOCHRON1 (ZmPLA1) gene, encoding a cytochrome P450 (CYP78A1), results in increased organ growth, seedling vigour, stover biomass and seed yield. The engineered trait is robust as it improves yield in an inbred as well as in a panel of hybrids, at several locations and over multiple seasons in the field. Transcriptome studies, hormone measurements and the expression of the auxin responsive DR5(rev): mRFPer marker suggest that PLA1 may function through an increase in auxin. Detailed analysis of growth over time demonstrates that PLA1 stimulates the duration of leaf elongation by maintaining dividing cells in a proliferative, undifferentiated state for a longer period of time. The prolonged duration of growth also compensates for growth rate reduction caused by abiotic stresses

Identification of a micropeptide and multiple secondary cell genes that modulate <i>Drosophila</i> male reproductive success

Even in well-characterized genomes, many transcripts are considered noncoding RNAs (ncRNAs) simply due to the absence of large open reading frames (ORFs). However, it is now becoming clear that many small ORFs (smORFs) produce peptides with important biological functions. In the process of characterizing the ribosome-bound transcriptome of an important cell type of the seminal fluid-producing accessory gland of Drosophila melanogaster, we detected an RNA, previously thought to be noncoding, called male-specific abdominal (msa). Notably, msa is nested in the HOX gene cluster of the Bithorax complex and is known to contain a micro-RNA within one of its introns. We find that this RNA encodes a "micropeptide" (9 or 20 amino acids, MSAmiP) that is expressed exclusively in the secondary cells of the male accessory gland, where it seems to accumulate in nuclei. Importantly, loss of function of this micropeptide causes defects in sperm competition. In addition to bringing insights into the biology of a rare cell type, this work underlines the importance of small peptides, a class of molecules that is now emerging as important actors in complex biological processes

Female x male interactions that shape reproductive success in Drosophila melanogaster

260 pagesSupplemental file(s) description: Chapter_5_S1, Chapter_4_S1, Chapter_3_S1, Chapter_2_S4, Chapter_2_S3, Chapter_2_S2, Chapter_2_S1.The meeting and fusion of gametes and the production of offspring are the main goals of sexually reproducing organisms. In internal fertilizers, fertilization success is enhanced by a suite of physiological and (at least in insects) behavioral changes that mated females undergo after copulation and exposure to the male’s ejaculate. However, conflicts within and between the sexes and context-dependent mating strategies maintain genetic variation in some molecules involved in reproduction. As a result, some combinations of female and male genotypes have a higher reproductive success than others; a phenomenon that could contribute to reproductive isolation as well as to idiopathic infertility in humans. Studies using Drosophila melanogaster elucidated several aspects of female x male genetic interactions that influence reproductive success. For example, natural variation linked with male seminal fluid proteins correlates with a male’s performance in sperm competition and his ability to induce egg production in his mate. However, the female’s genetic and molecular contributions to these interactions remain underexplored. I present four projects that have contributed to our understanding of the female’s side of female x male interactions. First, I employed natural variation in D. melanogaster in combination with transcriptome measurements to identify genes in females whose transcript levels are either altered by mating in general or are altered by mating in a female x male genotype-dependent manner. These experiments indicated that the transcript levels of immune response genes and genes with neuronal functions are especially sensitive to female x male genotype interactions. Second, my collaborator and I showed that these same groups of genes are also sensitive to interactions between the female’s microbiome and her mating status, indicating that not only genotype, but also environment (in this case the microbiome) can influence female x male interactions. Further, using transcriptome data, I detected male RNAs that were transferred to the female during mating. Finally, in a separate project, using sperm competition assays and tissue-specific candidate gene knockdown, my colleagues and I identified genes and neurons in females that influenced the paternity success of the first vs. second male a female mated with. Collectively, the results presented in this thesis encourage further investigation of RNAs in the male’s ejaculate and suggest that the female’s immune system and nervous system act as an important interface between the female and her mate.2022-06-0

Identification of a micropeptide and multiple secondary cell genes that modulate Drosophila male reproductive success

Even in well-characterized genomes, many transcripts are considered noncoding RNAs (ncRNAs) simply due to the absence of large open reading frames (ORFs). However, it is now becoming clear that many small ORFs (smORFs) produce peptides with important biological functions. In the process of characterizing the ribosome-bound transcriptome of an important cell type of the seminal fluid-producing accessory gland of Drosophila melanogaster, we detected an RNA, previously thought to be noncoding, called male-specific abdominal (msa). Notably, msa is nested in the HOX gene cluster of the Bithorax complex and is known to contain a micro-RNA within one of its introns. We find that this RNA encodes a "micropeptide" (9 or 20 amino acids, MSAmiP) that is expressed exclusively in the secondary cells of the male accessory gland, where it seems to accumulate in nuclei. Importantly, loss of function of this micropeptide causes defects in sperm competition. In addition to bringing insights into the biology of a rare cell type, this work underlines the importance of small peptides, a class of molecules that is now emerging as important actors in complex biological processes