Snapshots from Plant Biology 2020: Plant Reproduction

It’s been more than a month since the successful completion of the Plant Biology 2020 (PB20) Worldwide Summit hosted by the American Society of Plant Biologists (ASPB). But those who got to attend it certainly will not have come out of its daze yet. The conference, held for a good five days, came to the rescue to lift off pressure during a sombre time that had prolonged for months.

For an online, virtual conference that had over two thousand attendees, the sessions went fairly smoothly, with curious questions from the audience and stimulating discussions between researchers of diverse backgrounds. This would be a great time to reflect on some of the sessions that added stimulus to this amazing meeting.

Day two of the conference saw the session on reproductive development that had five speakers, one of whom presented a two-minute flash talk about her poster. Reproductive phase is a major and diverse part of a plant’s life cycle that is both biologically relevant as well as economically important. The talks presented reflected the many layers of plant reproductive cycle and weaved through the complexities that come with regulating the processes involved.

The session kicked off with Nathaniel Ponvert’s talk that sought to answer the question of when exactly during reproduction plants distinguish their own from other species. For a start, when a pollen tube makes contact with an ovule to discharge the sperm cells to effect fertilization, the synergid cells produce a unique pattern of spike in Ca2+ concentration, which is sensed by the proteins working downstream. Nathaniel’s work employed this Ca2+ signal pattern as a marker for pollen perception, which involved imaging the Ca2+ signals in synergid cells of plants expressing a Ca2+-specific biosensor. Utilizing the model plant Arabidopsis thaliana and its closer and more distant relatives, A. lyrata and Olimarabidopsis pumila, respectively, the work could establish that the distinction of ‘self’ from ‘non-self’ happens after the initial sensing of the pollen tube by proteins working downstream to the Ca2+ signal.

Graduating from ovule to seed, the next talk by Dr. Pinky Agarwal probed the function of a novel protein in seed development. Named SUPER STARCHY 1 (SS1), this seed-specific protein belonging to NAC family of transcription factors, was found to be a chief regulator of starch synthesis in rice grains, evident in the high starch accumulation in plants overexpressing it. In line with its role in reproductive phase, the overexpression plants were stunted and had underdeveloped vegetative phase. The interaction analyses revealed SS1 to bind to promoters of two genes encoding for vital seed storage proteins, and to repress their expression, hinting at its prominent role in regulating starch turnover in seeds.

Midway through the session, Ellen Zelinsky gave a peek into her poster, which deals with a polygalacturonase protein that is essential for normal floral development. Quite interestingly, mutant plants lacking this protein have flowers that have heavily altered structures, hinting at the importance of this single protein in floral organ patterning and development.

Moving on, the penultimate talk by Michael Nodine dwelt on how chromatin states of cells maintains the methylation of transposon through different development stages of plants. Michael smoothly sailed the audience through this seemingly complicated topic by explaining in detail all the layers of the work. His study demonstrated how changing states of chromatin, during different stages of plant development, helps transcription of non-coding small-interfering RNAs (si-RNAs), which regulate methylation of transposons in a feedback loop.