Factors Affecting the Number of Pollen Grains per Male Strobilus in Japanese Cedar (Cryptomeria japonica)

A standardized and efficient technique to estimate seed traits in plants with numerous small propagules

Premise

Variation in seed traits is common within and among populations of plant species and often has ecological and evolutionary implications. However, due to the time-consuming nature of manual seed measurements and the level of variability in imaging techniques, quantifying and interpreting the extent of seed variation can be challenging.

Methods

We developed a standardized high-throughput technique to measure seed number, as well as individual seed area and color, using a derived empirical scale to constrain area in Arabidopsis thaliana, Brassica rapa, and Mimulus guttatus. We develop a specific rational model using seed area measured at various spatial scales relative to the pixel count, observing the asymptotic value of the seed area as the modeled number of pixels approaches infinity.

Results

We found that our model has high reliability in estimating seed traits and efficiently processes large numbers of images, facilitating the quantification of seed traits in studies with large sample sizes.

Discussion

This technique facilitates consistency between imaging sessions and standardizes the measurement of seed traits. These novel advances allow researchers to directly and reliably measure seed traits, which will enable tests of the ecological and evolutionary causes of their variation.

A single-nucleotide substitution of CjTKPR1 determines pollen production in the gymnosperm plant Cryptomeria japonica

Pollinosis, also known as pollen allergy or hay fever, is a global problem caused by pollen produced by various plant species. The wind-pollinated Japanese cedar (Cryptomeria japonica) is the largest contributor to severe pollinosis in Japan, where increasing proportions of people have been affected in recent decades. The MALE STERILITY 4 (MS4) locus of Japanese cedar controls pollen production, and its homozygous mutants (ms4/ms4) show abnormal pollen development after the tetrad stage and produce no mature pollen. In this study, we narrowed down the MS4 locus by fine mapping in Japanese cedar and found TETRAKETIDE α-PYRONE REDUCTASE 1 (TKPR1) gene in this region. Transformation experiments using Arabidopsis thaliana showed that single-nucleotide substitution ("T" to "C" at 244-nt position) of CjTKPR1 determines pollen production. Broad conservation of TKPR1 beyond plant division could lead to the creation of pollen-free plants not only for Japanese cedar but also for broader plant species.