Since the very beginning of plant science, sexual plant reproduction (SPR) has proved an attractive and enduring topic for generations of botanists. With the rapid development of modern technology, a significant acceleration has occurred in our understanding on the developmental mechanisms of plant reproductive processes, particularly the evolution of double fertilisation, signalling in pollen tube orientation, molecular characterisation of plant gametes, maternal to zygotic transitions and parental gene involvement in early embryogenesis. This is reflected not only by several recent high-ranking research papers, but also by the frequent conferences and workshops on these topics. These include the 2008 XXth International Congress on SPR in Bras´齦ia and “Frontiers in SPR III” in Tucson, as well as “Cell-Cell Communication in Plant Reproduction” held in 2009 in Bath. The continuing efforts from around the world indicate that SPR is still a fertile and flourishing field, with great expectations for the coming decade.
Investigations on SPR have been enhanced recently by their underlying relationship to agriculture. With the development of molecular crop breeding comes an increasing requirement for knowledge on molecular mechanisms of SPR, both general regulatory processes, and in particular, signalling for cell-cell communication in several critical steps. To reveal mechanisms behind some well-known phenomena in modern agriculture, such as compatibility of crop crosses and fertility determination of remote hybrids and heterosis, one must first precisely understand the basic developmental processes and molecular mechanisms involved in SPR. Thus, it is not surprising that the field has attracted much attention in recent years. In fact, advances in the study of SPR throw new light on investigations for solving many existing problems in agriculture.
This special issue presents current research on multiple aspects of SPR, both pre- and post-fertilisation. Hence, this special issue of the Journal of Integrative Plant Biology features a diverse collection of papers. One paper, “The earliest normal flower in Liaoning Province, China” (see pages 800–811), presents evidence of component parts and morphology of early angiosperm flowers. Four papers, “A genome-wide functional characterisation of Arabidopsis regulatory calcium sensors in pollen tubes” (see pages 751–761), “GNOM-LIKE 2, encoding an ARF-GEF protein homologous to GNOM and GNL1, is essential for pollen germination in Arabidopsis” (see pages 762–773), “Regulation of actin dynamics in the pollen tubes:control of actin polymer level” (see pages 740–750) and “Pollen tube growth: a delicate equilibrium between secretory and endocytic pathways” (see pages 727–739), deal with molecular mechanisms of pollen tube growth and orientation, a hot field in SPR. Amongst these papers, Prof. Moscatelli offers a deep insight into dynamic control of vesicle trafficking in pollen tubes. In the signalling cascade of vesicle trafficking, calcium and actin dynamics play essential roles in the balance between secretory and endocytic pathways. GNOM-LIKE 2, as an ARF-GEF- and BFA-sensitive protein,may indirectly influence calcium and actin dynamics during pollen germination and pollen tube growth.
“Premature tapetum degeneration: a major cause of abortive pollen development in photoperiod sensitive genic male sterility in rice” (see pages 774–781) presents new evidence for the interaction between tapetum and pollen development. “Comparative detection of calcium fluctuations in single female sexual cells of tobacco to distinguish calcium signals triggered by in vitro fertilisation” (see pages 782–791) reports observations on calcium dynamics during sperm-central cell fusion, and “Oil body biogenesis during Brassica napus embryogenesis” (see pages 792–799) focuses on post-fertilisation developmental events, mainly on oil body generation and accumulation during embryogenesis in both wild type and mutants. A review paper, “Analyses of sexual reproductive success in transgenic and/or mutant plants” (see pages 719–726), gives a critical evaluation of current techniques used for investigating genes that affect pistil development, and provides useful information and technical guidance to readers in this field. These papers coherently address the common theme: development and its mechanisms in plant reproductive processes. In this way, we hope to create an atmosphere in which extensive discussion can stimulate and lead to interactions between scientists with different perspectives in order to inspire future directions.
We sincerely hope that this special issue of JIPB will provide a platform to highlight current advances and novel findings in the study of SPR. Finally, we express our appreciation to JIPB for supporting this special issue and to all authors for their great contributions. Mengxiang Sun, Professor The Editor for this Special Issue College of Life Sciences, Wuhan University, China