A cotton BURP domain protein interacts with α-expansin and their co-expression promotes plant growth and fruit production

Plant growth requires cell wall extension. The cotton AtRD22-Like 1 gene GhRDL1, predominately expressed in elongating fiber cells, encodes a BURP domain-containing protein. Here, we show that GhRDL1 is localized in cell wall and interacts with GhEXPA1, an α-expansin functioning in wall loosening. Transgenic cotton overexpressing GhRDL1 showed an increase in fiber length and seed mass, and an enlargement of endopleura cells of ovules. Expression of either GhRDL1 or GhEXPA1 alone in Arabidopsis led to a substantial increase in seed size; interestingly, their co-expression resulted in the increased number of siliques, the nearly doubled seed mass, and the enhanced biomass production. Cotton plants overexpressing GhRDL1 and GhEXPA1 proteins produced strikingly more fruits (bolls), leading to up to 40% higher fiber yield per plant without adverse effects on fiber quality and vegetative growth. We demonstrate that engineering cell wall protein partners has a great potential in promoting plant growth and crop yield.

β-expansins are divergently abundant in maize cultivars that contrast in their degree of salt resistance

Zea mays L. exhibits a strong growth reduction in response to NaCl-induced stress that is attributable to a decline of cell division and elongation. Wall-loosening expansins are of major impact for cell wall extensibility and growth. This study provides an analysis of the impact of an 8-d 100 mM NaCl stress treatment on the mRNA abundance of the α-and β-expansin sub-families using real-time quantitative RT-PCR. Moreover, we provide a comparative study of plants that contrast in their degree of salt resistance in order to reveal contrasting features of physiological functions that may bear a causal relation to the differential response of plants to salt. In result, the transcript abundance of wall-loosening β-expansins was impaired in size-reduced leaves of the salt-sensitive hybrid but not in leaves of the salt-resistant hybrid that maintained growth. This indicates a role for the β-expansins in processes related to salt resistance.