The major goals of modern agriculture are optimization and improvement of crops to sustain high productivity with minimal environmental impact. A variety of molecular methods have been developed for the regulation of trait-specific genes at the transcriptional and translational levels. Targeted post-translational modification for trait regulation is precisely done by microProteins which are involved in fine-tuning protein activity without altering overall plant structure and metabolism. MicroProteins(miPs) are small regulatory proteins with a single domain and size ranging from 5 to 20 kDa and they have their role in post-translational regulation of gene expression through protein-protein interactions. These proteins are referred to as ‘microProteins’ because of their small size and negative regulatory actions analogous to microRNAs (miRNAs)1. Deletions and duplications within genes encoding multidomain proteins have driven the evolution of single-domain proteins, which subsequently interact with their ancestral proteins from which they originated. It is hypothesized that microProteins and the proteins with which they interact have evolutionary relations3. Photoperiod‐dependent flowering in rice is regulated by transcription factor HEADING DATE 1 (Hd1), which acts both as an activator and repressor of flowering in a daylength-dependent manner. An investigation was carried out using microProteins as a tool to modify rice sensitivity to the photoperiod by designing a synthetic Hd1 microprotein (Hd1miP) capable of interacting with Hd1 protein and overexpressing it in rice. Transgenic OX‐Hd1miP plants flowered significantly earlier than wild-type plants when grown in long-day conditions. These results show the potential of microProteins to serve as tools for modulating crop traits and unravelling protein function2.

Using the synthetic microProtein approach an investigation was carried out on multidomain proteins of different classes. It has revealed that multidomain proteins like DCL1, BRI1, and CRY1 can be regulated by overexpressing their protein-protein interaction domains as synthetic microProteins. These results show that microProteins can inhibit any multidomain protein containing a protein-protein interaction domain1.

The advances in analytical, molecular, and computational methods have helped to expand the pool of miPs characterized across species. However, there is a lot to know about the cellular dynamics and specificities concerning the miPs. MicroProteins offer exciting potential for plant breeding due to their targeted regulation and small size, allowing for easier manipulation. However, their precise functions and effectiveness in complex traits remain a challenge. Ongoing research focuses on identifying and characterizing novel microProteins and developing techniques for their precise manipulation in breeding programs.

References:

1DOLDE, U., RODRIGUES, V., STRAUB, D., BHATI, K. K., CHOI, S., YANG, S.W. AND WENKEL, S., 2018, Synthetic MicroProteins: versatile tools for post-translational regulation of target proteins. Plant Physiol., 176: 3136-3145.

2EUGEN, T., ARIZA, J. G., BRAMBILLA, V., SUN, B., BHATI, K. K., FORNARA, F. AND WENKEL, S., 2020, Control of flowering in rice through synthetic MicroProteins. J. Integr. Plant Biol., 62: 730-736.

3HARSHITHA, B. S., MANJUNATH, K. K. AND BHARGAVI, H. A., 2023, Mysterious MicroProteins as a novel tool for crop improvement: A review. Pharma Innov., 12(1): 2317-2322.